I toyed with Yuri's TPC simulation curve and I show you just one result:
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BTW, the ALTRO parameters were:
K1 12807
K2 50251
K3 64797
L1 65145
L2 54317
L3 8537
-- Tonko
Please attach any information about the Fast Cluster Finder (FCF) here.
I am sending a short description of the TPX cluster finder flags. This is more an Offline issue but I guess this is a better group since it is a bit technical. 1) The flags are obtained in the same way other variables such as timebin and pad are obtained. I understand that this is not exported to StHit *shrug*. See i.e. StRoot/RTS/src/RTS_EXAMPLE/rts_example.C 2) They are defined in: StRoot/RTS/src/DAQ_TPX/tpxFCF.h The ones pertaining to Offline are: FCF_ONEPAD This cluster only had 1 pad. Generally, this cluster should be ignored unless you are interested in the prompt hits where this might be valid. The pad resolution is poor, naturally. FCF_MERGED This is a dedconvoluted cluster. The position and charge have far larger errors than normal clusters. FCF_BIG_CHARGE The charge was larger than 0x7FFF so the charge precision is lost. The value is OK but the precision is 1024 ADC counts. Good for tracking, not good for dE/dx. FCF_BROKEN_EDGE This is the famous row8 cluster. Flag will disappear from valid clusters once I have the afterburner running. FCF_DEAD_EDGE Garbage and should be IGNORED! This cluster touches either a bad pad or an end of row or is somehow suspect. I need this flag for internal debugging but the users should IGNORE those clusters! -- Tonko
I commited the "padrow 8" afterburner to the DAQ_TPX CVS directory. If all runs well, you should see no more peaks on padrow 8. The afteburner runs during the DAQ_READER unpacking. However, please pay attention to the cluster finder flags which I mentioned in an email ago. Specifically: "FCF_DEAD_EDGE Garbage and should be IGNORED! This cluster touches either a bad pad or an end of row or is somehow suspect. I need this flag for internal debugging but the users should IGNORE those clusters!" -- Tonko
This page is for information regarding shorts or current anomalies in the TPC field cages.
The attached powerpoint file from Blair has plots of the excess current seen in the IFC East for 2006.
This can be seen in the following plot, where I again show the distortion to laser tracks at a radius of 60cm (approximately the first TPC padrow) versus Z in the east TPC using distored run 7076029 minus undistorted run 7061100 as red data points. Overlayed are curves for the same measure from models of a half-resistor short (actually, 1.14 MOhm short as determined by the excess current of ~240+/-10nA [a full 2MOhm short equates to 420nA difference]) located at rings 9.5, 10.5, ..., 169.5, 179.5 (there are only 182 rings).
[note: earlier plots I have shown included laser data at Z = -55cm, but I've found that the laser tracks there weren't of sufficient quality to use; I've also tried to mask off places where lasers cross over each other]
The above plot points towards a short which is located somewhere among rings 165-180 (Z < -190cm). As the previous years' shorted rings were rings 169 and 170 ( = short at ring 169.5), it seems highly likely that the present short is in the same place. More detail can be seen by looking at the actual laser hits. The first listed attached file shows the laser hits as a function of radius for lasers at several locations in Z. The dark blue line is a simple second order polynomial fit I used to obtain the magnitude of the distortion at radius 60cm, which I used in the above plot. The magenta line is the model of the half-resistor short at ring 169.5, and the light blue line is the same for ring 179.5 (the bottom two curves on the above plot). Either curve seems to match the radial dependence fairly well.
Further refinement can be achieved by modeling the exact resistor chain. We have a permanent short at ring 169.5 (rings 169 and 170 have been tied together), and have replaced the two 2MOhm resistors between 168-169 and 170-171 with two 3MOhm resistors (see the attached photo of the repair, with arrows pointing to candidate locations for shorts via drops of silver epoxy). So it is more likely that we have a 1.14MOhm short on one of these two 3 MOhm resistors. The three curves in this next plot are:
We can also take a look at the data with the resistor in. Here is the same plot as before with a 1.14MOhm short at the same locations, but with an additional compensating resistor of 1.0MOhm. The fact that all the data points are below zero points again towards a short near the very end of the resistor chain, preferring a location of perhaps 177.5 over shorts near ring 170. These plots do not include the use of the 3MOhm resistors, but that difference is below the resolution presented here.
Zoom in with finer granularity between rings (every other ring short shown):
The second listed attached file shows the laser hits as a function of radius for lasers at several locations in Z for the case of the resistor in, again with magenta and blue curves for the model with shorts at ring 169.5 and 179.5 respectively.
170.5 | 171.5 | 175.5 |
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Gene Van Buren
gene@bnl.gov
In terms of momentum distortion, a 1mm distortion at the outermost padrows would cause a sagitta bias of perhaps about 0.5mm for global tracks (and even less for primary tracks), corresponding to an error in pt in full field data of approximately 0.006 * pt [GeV/c] (or 0.6% per GeV/c of pt). This is certainly at the level where it is worthwhile to try to fix the distortion if we can figure out where the short is. It is also at the level where we should be able to see with the lasers perhaps to within 50cm where the short is.
Just as a further point of reference, the plot for radius = 189cm, corresponding to the radius of the outermost padrow in the middle of a sector (its furthest point from the OFC) can be found here.
This possible distortion remains uninvestigated at this time.
Gene Van Buren
gene@bnl.gov
Also perhaps worth noting is that the 1.0MOhm compensating resistor probably helps reduce the distortions even more than an exact 1.14MOhm would. The latter causes the distortions not to change between the short location and the central membrane, but the former actually causes the distortion to re-correct the damage done between the short location and the endcap!
Compensating resistance [MOhms] |
Distortion on first padrow vs. Z |
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0.0 |
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1.0 |
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1.14 |
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2.0 |
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4.0 |
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20.0 |
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Gene Van Buren
gene@bnl.gov
No compensating resistor (run 7076029):
With 1 MOhm compensating resistor (run 7076032), which brings IFC east current to correct value within ~20 nAmps, according to 10:27am 2006-03-17 entry in Electronic ShiftLog:
Again, I looked at the distortion as seen be comparing TPC hits from the distorted runs to those from an undistorted run as I did at the beginning of this page (but this time taking distorted minus undistorted). For the undistored, I again have only run 7061100 to work with as a reference. The plots for each Z are in the second listed attached file below, where the top 6 plots are for the no-compensating-resistor run (7076029), and the bottom 6 are the same ones with the resistor in. I also put on the plots the value of the difference from a simple fit (meant only to extract an approximate magnitude) at a radius of 60cm (approximately the first TPC pad row). Those values are also presented in the following plot as a function of Z, confirming the improvement of the distortion with the resistor in place.
These plots seem to point at a short which is occurring somewhere between the lasers at Z = -145 and -115cm.
Gene Van Buren
gene@bnl.gov
After ring 181, the potentials are determined by a box of resistors which sit outside the TPC. This is well documented, but at the time of this writing is not complete. This was particularly relevant during Run 9 when an electrical short developed inside the TPC between rings 181 and 182 of the outer field cage on the west end (OFCW). Shown here is a plot of the resistors:
Note that the ammeter is essentially a short to ground, while the voltmeters are documented in the Keithley 2001 Manual to express over 10 GOhm of resistance (essentially infinite resistance). The latter only occurs when the input voltage is below 20 V. The voltages at rings 181 and 182 are above 20 V and below 200 V (though actually at negative voltage), so their voltage is scaled by the shown 1.11 and 10.0 MOhm resistors to be stepped down by a factor of x10. The readings are then multiplied by x10 before being recorded in the Slow Controls database.
After Run 9, this box was disconnected and resistances were measured for the OFCW portion. Because the resistors were not separated from each other, equivalent resistances were actually measured. In the below math, R182eq refers to the resistance measured across resistor R_182, while Rfull is the resistance measured between the input to the box from ring 181 to the output for the ammeter. R111 is the combined 10 + 1.11 MOhm pair.
double R111 = 10.0 + 1./(1./1.11 + 1./10000.) 11.11 double R182eq = 0.533 // measured double Rfull = 2.31 // measured double pa = R111 - Rfull double pb = R111*(R111 - 2*Rfull) double pc = (R182eq - Rfull)*R111*R111 double R181 = (-pb + sqrt(pb*pb - 4*pa*pc))/(2*pa) 2.3614 double R182 = 1./(1./R182eq - 1./R111 - 1./(R181+R111)) 0.5841 double R182b = 1./(1./R182 + 1./R111) double Vcm = 27960. double Rtot = 364.44 // full chain double Inorm = Vcm/Rtot 76.720 double V181_norm = Rfull * Inorm 177.22 double V182_norm = V181_norm * R182b/(R181 + R182b) 33.724 double Rshorted = 1./(1./R111 + 1./R182 + 1./R111) 0.5286 double Rmiss = Rfull - Rshorted 1.7814 double Ishorted = Vcm/(Rtot - Rmiss) 77.097 double V181_short = Rshorted * Ishorted 40.750 double Iexcess = Ishorted - Inorm 0.377
Note that many of these numbers would be different for the inner field cages.
External resistors to make up for missing resistance can also be added to the chain here.
See PPT attachment for simulations of floating grid wires from Nikolai Smirnov which show that the data is consistent with two floating -190V wires in sector 8, and two floating -40V wires in sector 3 (all wires are at -115V when the grid is "open").
Using the code in StMagUtilities, these are maps of the GridLeak distortion.
First, this is a basic plot of the distortion on a series of hits going straight up the middle of a sector (black: original hits; red: distorted hits). The vertical axis is distance from the center of the TPC (local Y) [cm], and the horizontal axis is distance from the line along the center of the sector (local X). Units are not shown on the horizontal axis because the magnitude of the distortion is dependence on the GridLeak ion charge density, which is variable.
The scale of the above plot is deceptive in not showing that there is some distortion in the radial direction as well as the r-phi direction. The next pair of plots show a map of the distortion [arb. units] in the direction orthogonal to padrows (left) and along the padrows (right) versus local Y and angle from the line going up the center of the sector (local φ) [degrees].
One can see that the distortion is on the order of x2 larger along the padrows than orthogonal to the padrows. Also, it is clear that there is a small variance in magnitude of the distortion across the face of the sectors.
The next plot shows the magnitude of the distortion [arb. units] along the padrow at the middle of the sectors vs. local Y [cm] and global Z [cm]. The distortion is largest near the central membrane (Z=0) and goes to zero at the endcaps (|Z| ≅ 205 cm), with a linear Z dependence in between, which flattens off at the central membrane and endcap due to boundary conditions that the perturbative potentials are due to charge in the volume and are constrained to zero at these surfaces.
Data for STAR TPC supersector. 05.05.2005 07.11.2005 Jon Wirth, who build all sectors provide these data. Gated Grid Wires: 0.075mm Be Cu, Au plated, spacing 1mm Outer Sector 689 wires, Inner Sector 681 wires. Total 1370 wires per sector Cathode Grid Wires: 0.075mm Be Cu, Au plated, spacing 1mm Outer Sector 689 wires, Inner Sector 681 wires. Total 1370 wires per sector Anode Grid Wires:0.020mm W, Au plated, spacing 4mm Outer Sector 170 wires, Inner Sector 168 wires. Total 338 wires per sector Last Anode Wires: 0.125mm Be Cu, Au plated Outer Sector 2 wires, Inner Sector 2 wires. Total 4 wires per sector
We are most interested in the gap between Inner and Outer sector, where ion leak is important for space charge. On fig. 1 wires set is shown. The distance between inner and outer gating grid is 16.00 mm. When Grid Gate is closed, the border wires in Inner and Outer sectors have -40V, each next wire have -190V and after this pattern preserved in whole sector - see fig. 2. When gating grid is open, each wire in gating grid have the same potential -115V. Above grid plane we have a drift volume with E~134V/cm to move electrons from tracks to sectors and repulse ions to central membrane. Cathode plane has zero voltage, while anode wires for outer sector holds +1390V and for inner sector +1170V.
Fig. 1. Wire structure between Inner and Outer sector.
Fig.2 Voltages applied to Gating Grid with grid closed.
Another configurations of voltages on gating grid wires are presented on fig.3. All these voltages are possible by changing wire connections in gating grid driver. Garfield simulations should be performed for all to find a minimum ion leak.
Fig.3 Different voltages on closed gating grid (top: inverted, bottom: mixed).
This is a key for Nikolai's files: there are 4 sets of files in each set there is simulation for Gating Grid voltages on last wires. Additionally he artificially put a ground shield on the level of cathode plane and simulated collection for last-thick anode wire and also ground shield and last thin anode wire.
Setups: | Standard | Inverted | Mixed | Ground Strip | Ground Strip and Wire |
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Electron paths | PS![]() |
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Ion paths (inner sector) |
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Ion paths (outer sector) |
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First note: the ever-present problem that our model goes to zero distortion at the endcaps, while the measured distortions do not appear to do so (though the distortion curves should flatten out [as seen in the above plots] as a function of Z near the endcap and central membrane due to boundary conditions on the fields in the TPC).
Second note: I have not excluded sector 20 from these plots, which is partly to explain why the east half (z<0) has slightly less distortions than the west in these profile plots. In reality, east and west were about even for a normal run (distortions excluding sector 20).
Here is the z-phi plot for Low (it's almost difficult to see the distortion reduction in the z-phi (in "o'clock") plot for Half):
Third note: (though not too important for this study because we generally ignore east/west comparisons) the sectors between 1-6 o'clock already tend to show somewhat less distortion than the sectors at 7-12 o'clock, and because it is true on both halves of the TPC, it is more likely to be due SpaceCharge azimuthal anisotropy than asymmetries in the endplanes. Here are the distortions at |z|<50 for east (red) and west (blue) as a function of phi in "o'clock" where one can see the already present asymmetry, explaining why sectors 1-6 are already less distorted in the Norm run than sectors 7-12:
We have to normalize to sectors 7-12 to see the drop in distortions as it the runs are taken at different times when the luminosity of the machine, and therefore the distortion normalizations, are different. Here are the ratios from sectors 1-6 / sectors 7-12:
And the double ratios to see the drop in the Half and Low runs w.r.t. the Norm run:
These plots show ratios in the Z = 25-150cm range of about 0.86 and 0.59 respectively, or reductions of about 14% and 41% give or take a few percentage points. Data beyond 150cm tends to be poor and there's little reason to believe that the ratio really changes by much there. However, there does appear to be some shape to the data, which is not understood at this time.
Another way to calculate the difference in distortions is to take a linear fit to the slope of the distortions between z = 25-150cm. Those fit slopes are:
Low: 1-6: 0.000250 +/- 0.000019 7-12: 0.000420 +/- 0.000024 Half: 1-6: 0.000365 +/- 0.000023 7-12: 0.000433 +/- 0.000025 Norm: 1-6: 0.000401 +/- 0.000024 7-12: 0.000422 +/- 0.000023Again, we need the ratio of ratios:
[Half(1-6)/Half(7-12)] / [(Norm(1-6)/Norm(7-12)] = 0.89+/-0.11 (12%) [Low(1-6)/Low(7-12)] / [(Norm(1-6)/Norm(7-12)] = 0.63+/-0.08 (12%) Inner reduction = (11 +/- 11)% Outer reduction = (26 +/- 11)% Total reduction = (37 +/- 8)%These numbers are smaller than the reductions indicate by the above plot of double ratios of the distortions themselves. This likely reflects the errors in fitting the slopes. In that sense, the plot values may be more accurate. We need not worry in this study about getting the reduction numbers exact, but it is perhaps accurate enough to say that the inner sector gain drop reduces the distortion by about 13%, and the outer sector gain drop reduces it further by about 27% (about twice as much as the inner) from the original distortion. It is clear that both inner and outer TPC sectors contribute to the distortion, and that the outer TPC contributes significantly more to the distortion. If hardware improvements can only be implemented for either the inner or outer, then the outer is the optimal choice in this respect. It is not obvious offhand whether this is consistent with the GridLeak Simulations which we have done so far for these ion leaks.
Present at the meeting(s) were: myself (Jerome Lauret), Alexei Lebedev, Yuri Fisyak, Jim Thomas, Howard Wiemann, Blair Stringfellow, Tonko Ljubicic, Gene van Buren, Nikolai Smirnof, Wayne Betts (If I forgot anyone, let me know).
It is noteworthy to mention that the TPC future was initially addressed at the Yale workshop in (Workshop on STAR Near Term Upgrades) where Gene van Buren gave a presentation on TPC - status of calibration, space charge studies, life time issues. While the summary was positive (new method for calibration etc...) the track density and appearance of new distorsions as the lumisoity ramped up remained a concern. As a reminder, we include here a graph of the initial Roser luminosity projection.
which was build from the following data2002 | 2003 | 2004 | 2005 | 2006 | 2007 | 2008 | 2009 | 2010 | 2011 | 2012 | 2013 | 2014 | |
Peak Au Luminosity | 4 | 12 | 16 | 24 | 32 | 32 | 32 | 32 | 32 | 48 | 65 | 83 | 83 |
Average Au Store Luminosity | 1 | 3 | 4 | 6 | 8 | 8 | 8 | 8 | 16 | 32 | 55 | 80 | 80 |
Total Au ions/ring [10^10] | 4 | 8 | 10 | 11 | 12 | 12 | 12 | 12 | 12 | 12 | 12 | 12 | 12 |
An update summary of the status of the TPC was given by Jim Thomas at our February
2005 collaboration meeting (A brief look at the future evolution of TPC
track distortions ; see attachement below) to adress ongoing GridLeak
issues. Slide 19 summary for teh future is added here:
Will the TPC Last Forever?
Probably of academic interest
Questions arose as per the liability of the detector itself i.e., aging issues (including shorts and side effects) were raised along with increasing concerns related to grid leak handling. Alexei Lebedev proposed a serie of hardware modification in May 2005 to account for those issues (see What we can do with TPC while FEE are in upgrade attachement).
Relevant to possible software and hardware solutions for the grid leak are GridLeak Simulations of the fields and particle paths in the region near the inner/outer TPC sector gap.
Extensive analysis are also available from the pages SpaceCharge and GridLeak and especially (for AuAu) this page QA: High Luminosity and the Future.
See the attached file: RD51-Note-2009-002.pdf
Studies of SpaceCharge in the TPC.
Here I show the expected distortions in the STAR TPC as represented by the pointing error of tracks to the primary vertex (otherwise known as the DCA) due to experienced (star symbols) and projected luminosities (triangle and square symbols) at RHIC. One can think of these distortions as being caused by the accumulated ionization in the TPC due to charged particles traversing it from collisions (ignoring any background contributions), or the charge loading of the TPC.
These measurements and projections are current as of November 2008 with the exception of the pp500 (pp collisions at √s = 500 GeV) projections (open symbols) [1,2]. In 2005 the expectation was that RHIC II could achieve pp200 peak luminosities of 150 x 1030 cm-2sec-1 and pp500 peak luminosities of 750 x 1030 cm-2sec-1 [3]. Presently (2008), the pp200 peak luminosity estimate at RHIC II has dropped to 70 x 1030 cm-2sec-1, and this is what is used in my plot. I have found no current estimate for pp500. The 2005 estimate indicated a factor of x5 more peak luminosity from the 500 GeV running than 200 GeV; I do not know if that is still possible, but I have chosen to use only a factor of x2 (should be conservative, right?) in the plot shown here.
I have also had to estimate the conversion of luminosity into load in the TPC for pp500 as we have not yet run this way. We did run at √s of approximately 405 GeV in June 2005, which showed a 17% increase in load over pp200 per the same BBC coincidence rate [pp400 (2005)]. I have roughly estimate that this means approximately a 25% increase in TPC load going from pp200 to pp500, with no serious basis for doing so.
Finally, the documented projections show that RHIC II will achieve approximately a factor of x2.6 increase over RHIC I for both AuAu200 and pp200 [2]. I have taken the liberty to apply the same factor of x2.6 to CuCu200, dAu200, and pp500.
(Note: The pp data use a different horizontal axis which was adjusted to lie amidst the ion data for ease of comparison, not for any physically justified reasons.)
Of the data we've taken so far, AuAu collisions have presented the highest loading of the TPC. However, CuCu collisions have the potential to introduce the highest loading for ions, and the RHIC II projections lead to pointing errors close to 20 cm! Actually, SiSi may be even worse (if we ever choose to collide it), as the luminosity is expected to achieve a factor x4.2 higher than CuCu, while the load per collision may be in the 40-50% ballpark of CuCu [2,3].
Loading due to pp collisions at 200 GeV are generally similar to AuAu collisions at 200 GeV, but 500 GeV pp collisions will load the TPC much more severely. Even in RHIC I, we may have pointing errors between 5-10 cm using my conservative estimate of x2 for the luminosity increase over pp200. If the factor of x5 is indeed possible, then use of the TPC in pp500 at RHIC II seems inconceivable to me, as the simple math used here would completely break down (the first TPC padrows are at 60cm, while 2.5*25.1 cm is larger than that)**. Even with a factor of x2, things may be quite problematic for pp500 in RHIC II.
References:
Some additional discussions from 2005 regarding the TPC and increased luminosities are documented at Long term life time and future of the STAR TPC.
Note: This is an update of essentially the same plot shown in the 2007 DAQ1000 workshop (see page 27 of the S&C presentation).
** Actually, a rather major point: we never get full length tracks with DCAs to the primary vertex of more than a couple cm anyhow, due to the GridLeak distortion. These tracks get split and the DCAs go crazy at that point. Since GridLeak distortion corrections are only applied when SpaceCharge corrections are, an roughly appropriate SpaceCharge+GridLeak correction must be applied first to even find reasonably good tracks from which to determine the calibration.
In Run VIII, dAu data was acquired at high enough luminosities to worry about SpaceCharge (it was ignored previously in the Run III dAu data (2003)). Attached is initial work by Jim Thomas to determine the charge distribution in dAu.
TPC Sector Alignment Using Particle Tracks for Run 8
Provide link to minutes of meetings held.
Earlier minutes from during construction and commisioning can be found on https://drupal.star.bnl.gov/STAR/subsys/upgr/itpc/itpc-meetings/itpc-minutes
Started on 10/14/2020; but it has not been strictly kept up to date.
March 23, 2023
Friday: East side was finished
from Christian
March 16, 2023
TPC meeting March 16,2023
Present: Gene, Tommy, Yuri, Alexei, Jim and Flemming
-Hardware
Alexei complete East laser alignment; Laser system is now ready for upcoming run
Next week will install ‘new’ magnetic sensors for additional monitoring.
Q: can these be interfaced to Slow Control (Monitoring)
- Electronics
- The TPX s8-3 RDO issue turned out to be a network card problem in the DAQ PC. West is ok a few FEEs are masked off for run
- East TPC should also be ready.
Gating grid tests
- Gene is proposing that we test the effectiveness (transparency) of the GG under different beam conditions.
- Aim to take short runs (<1 min) with 2,3,4,5kHz rate for MB data taking and similar for High lumi running later in the runs.
- Gene will talk to Jeff on setting up run configs so it can easily be run by crew. And with JG on beam conditions.
- The equest will be added to the TPC reafiness status
Pre run calibrations
Had long discussion on FF/RFF information that should be extracted. STAR magnet is currently wired for FF.
Yuri would like, now that Alexei has installed detector to monitor possible movement , that we switch a couple of times between FF , 0 , and RFF to see if a) there is a movement and b) if it is reproduceable. This does not need COSMIC data
It was not clear how this knowledge would translate into improved calibrations of TPC. Jim pointed out that (some) E-B mis alignment is already included in space charge distortions (static?). Gene commented that the main geometry calibration issue/uncertainties is related to the super sector to super sector alignment.
Yuri iterated that understanding if there are movements of TPC between FF and RFF will help for calibrations methods.
WWill bring the proposal up at readiness for TPC, but expect to get push back to the ‘cost’ (time, people,..) of doing multiple filed switches.
De/dx calibrations
Yuri pointed to the presentation at last S&C meetins that identified at FF/RFF difference between a correction that has been used previous for de/dx vs. position along wire attributed to wire to pad plane diff. See https://drupal.star.bnl.gov/STAR/system/files/RunXXI%20OO200GeV.pdf
FV raised the issue why this shows up in OO at 200 GeV which has about equal positive and negative charge tracks with opposite curvatures.
+ Run 21 dAu200 SpaceCharge
- Babu continues to find essentially no asymmetry between east and west, despite historically seeing ~20% more in east
- Gene sees asymmetry in the lower luminosity Run 21 dAu data, but it disappears at high luminosity
- Recommendation from Gene was for Babu to process more high luminosity data to help investigate dependencies further
- Run 22 pp500 SpaceCharge
- Babu has plenty of SpaceCharge work to do even without Run 22, plus his physics analysis
- Gene has asked the PWGs to provide an additional helper to investigate possible fill-by-vill variations as seen in Run 17
- Good to educate more people about SpaceCharge anyhow, even if Babu does find time to work on it
+ New cluster finder
- Tonko expects it to be not just different, but "better"
- Tommy proposed a test with embedding to see if momentum resolution and acceptance improves as Tonko hopes
- Yuri suggests not to focus on momentum resolution, but rather efficiency
- Tommy will discuss with Tonko more
+ dE/dx adjustments by analyzers
- Tommy brought up artificial, empirical dE/dx nsigma shifting by analyzers for BES-I datasets
- Yuri says that's ok as a band-aid for older productions of iTPC era data, but that the new dE/dx model introduced last year should help avoid this
- Tommy is willing to work on a standard version of the empirical band-aid for people to use, and no one objected
March 9, 2023
February 23, 2023
February 16, 2023
February 9, 2023
Feb 9, 2023 TPC meeting
Present: Yuri, Prahsanth, Alexei, Flemming, Tommy
--hardware
Westpole installed. #d sensor installed before and can be viewed so we can observe movement when filed is turned on, changed polarity etc.
Water leak in East laser box. Alexei will investigate.
- After insertion 2 bad FFEs identified. Likely due to squeezed cable. Need to ensure better pre-closure inspection for future years.
Software
Tommy and Tonko identified one source of differences between online and offline clusters. Namely simulation of hardware asic that merged time sequences separated by just one empty timebin (below threshold) would be merged into one
Yuri reported that analysis of recent survey revealed that TPC is rotated relative to RFF.
Still needs to talk to survey group to understand coordinate systems.
Yuri reported (see meeting page) that the QA plots for pbar vs p vs pt for the period c (production nomenclature) ie. From after covid shutdown is different than before shutdown, Period “” and b .
January 25, 2023
January 11, 2023
January 4, 2023
December 21, 2022
Present: Alexei, Yuri, Guannan, Tommy, Gene, Flemming, Irakli, and myself
== Hardware
— survey done on west but not east side
— Alexei (currently on vacation) trying to push a little to get it done
— found good way to put cameras for TPC movement
— Alexei will prepare short presentation upon return == Electronics
— inner sector RDOs on west side have been put backup by Alexei
— but on east side some RDOs still need to be returned to proper position — Alexei needs to talk to Tonko about east side before Tonko resumes work with RDOs on or after 1/1/23
== Software
— Gene mentions that Babu is still facing some issues on SC and GL
— PWGs now prioritizing O+O
— SC is ongoing for that but Babu needs some help from Gene
— once that’s done will move forward with TPC dE/dx etc.
— Irakli working on alignment, RFF seems to be converged
— FF does not seem to be in right place in X after RFF convergence (within 100 um)
— Yuri finished with dE/dx calibration (7.7 and 9.2 from 2020)
— have put calibration constants from new model in dB
— need final check with Standard Library
— Guannan is continuing work on deep tuning of TpcRS
— some problems observed
— Tommy continuing with offline/online cluster comparison
— 0.5% difference observed and must be understood
December 14, 2022
No meeting, but Yuri presented an update on dE/dx at the s&c meeting - presentation
Electronics status presented by Tonko at analysis meeting - presentation
December 7, 2022
November 30,2022
November 16, 2022
November 09,2022
November 02, 2022
present:
Gene, Yuri, Tommy, Alexei, Chenlian Jin, Flemming
excused: Richard
Alexei; working on probes for survey.
Open questions cosmics for survey field A/B before run?
Gene: There is no progress on space charge for some BesII years: dAu, 17.6 GeV FXT
Also need for run 22
Will contact Temple.
Nhits issues solved. Will pay more attention to cluster status when selecting/counting cluster distributions
Yuri:
a) will wrap up de/dx model for higher Z. Couple of weeks.
Request that we have a presentations for model before presenting to collaboration.
b) There is interest in making common PID (de/dx,btof,etof,...) for BESII data set from Rice group. Will like to use tpc meetings and e-mail list for this activity.
Suggestions add and invite this group
October 26, 2022
October 19,2022
October 5, 2022
August 17, 2022
Hardware update,
More on de/dx for 7.7 GeV auau
update from Alexei of TPC electronics readiness
About 2-3 weeks ago we had power dip and since I not paid attention to platform. I found some TPC VME crates and TPC FEE VME were OFF. I powered FEEs from platform(all PS have green LEDs) and control room, everything looks OK, but red LEDs on TPX PCs: 2, 24, 25-36 remained red.
August 10, 2022
July 27, 2022
Present: Alexei, Yuri, Gene, Tommy, and myself
== Software
— some slides on current state of dE/dx model work
— will be updated as work progresses
— will post slides with current status (keeping in mind there is more to do)
-- see https://drupal.star.bnl.gov/STAR/system/files/Revison%20STAR%20TPC%20dEdx%20Model.pdf
July 7, 2022
Hardware update. Survey done, Short repaired,
Software de/dx modle update
minutes
June 29, 2022
hardware update. Prepare for survey. Concern for Ar availability
software Tommy,Yuri have been comparing cluster finders offline/online
minutes
June 22, 2022
Hardware update, survey. TPC electronic speedupgrade, repair status
software update
minutes
June 15, 2022
Updates on survey plans
minutes
June 8, 2022
Updates on old vs. new cluster finder, simulated charge distribution from fixed target
minutes
June 1, 2022
Updates on dE/dx work, old vs. new cluster finder, simulated charge distribution from fixed target
minutes
May 18, 2022
TPC survey delay, inner sector wires, electronics update, 7.7 dE/dx work
minutes
May 11, 2022
gap measurments, 3D sensor prep work, inner sector wires, electronics update, 7.7 dE/dx work
minutes
April 27, 2022
nitrogen switchover, 3D sensor prep work, spare inner sectors, space charge corr., 7.7 dE/dx work
minutes
April 20, 2022
survey results, electronics status end of run, 7.7 de/dx calib done
minutes
April 7, 2022
prep for FF/RFF survey, space charge corr, updated manuals
minutes
February 2, 2022
discussion on added CF4 to TPC, methane shortage, run19 FEE status tables complete
minutes
January 12, 2022
to from run22 submitted, many RDO failures, look at skipping alt row for reco (pp500)
minutes
December 1, 2021
Analysis of shorts, laser response, tpc blower fixed
minutes
November 24, 2021
Some results from short measurements, Open issues ahead of run, missing Vdrift for a day.
minutes
November 17, 2021
Magnetic field settings reading GG slow control layout, short discussion, variable vdriftd
minutes
November 10, 2021
Plan for measurements for field cage short,
minutes
November 3, 2021
West field cage short; run 19 space charge; upcoming calibration issues.
minutes
October 27, 2021
TPC electronics status (Tonko), Laser West repaired, 19.2 GeV space charge nearly complete.GG slow control.
minutes
October 20,2021
hardware status, GG driver, calibration update(Yuri) see slides
minutes
October 13, 2021
hardware status, cosmic request for run22 startup
minutes
September 22,2021
9.2 TPC space charge cal completed,
Embedding issue for FXT Xianglei discussed.
minutes
September
September 8, 2021
brief meeting ; hardware cathode control
minutes
September 1, 2021
minutes
August 25, 2021
NMR status, laser progress
de/dx short term time dependence, helpers for calibration
minutes
August 18 no meeting
August 11, 2021meeting link
agenda: hardware, calibration and software update
August 4, 2021 meeting link
agenda:
- hardware status
-- gating grid
- calibrations
- TPC tasks for calibrations, software maintenance
-- presentations on meeting link
minutes -
December 9, 2020
Agenda:
-hardware status
- software
--- alignment progress
--- https://drupal.star.bnl.gov/STAR/system/files/he34embedding4th.pdf
--- AOB
meeting link: https://drupal.star.bnl.gov/STAR/event/2020/12/09/tpc-weekly
December 2, 2020
agenda hardware status
meeting link and minutes : https://drupal.star.bnl.gov/STAR/event/2020/12/09/tpc-weekly
November 18, 2020
agenda:
hardware - SF4 tests; laser system
software; 3He efficeincies, track splitting - see talk on meeting event page
aignment progress
meeting place: https://drupal.star.bnl.gov/STAR/event/2020/11/18/tpc-weekly
November 6, 2020
Discussion points:
TPC power cables
Installation of Gating Grid reinstallation
Presentation on 3He efficiencies
Clusterfinder offline vs online
meeting place https://drupal.star.bnl.gov/STAR/event/2020/11/04/tpc-weekly
October 28, 2020
Discussion points:
hardware: TPC gas investigation; electronics repair
software: GG turnon effects
meeting place https://drupal.star.bnl.gov/STAR/event/2020/10/28/tpc-weekly
October 21, 2020
Discussion points:
hardware: gating grid driver
software: Super sector alignment procedure
meeting page https://drupal.star.bnl.gov/STAR/event/2020/10/21/tpc-weekly
October 14, 2020
Discussion points
Hardware: TPX sector 13,14 powersupply cable repairs
Software: Super sector alignment procedures
meeting page https://drupal.star.bnl.gov/STAR/event/2020/10/14/tpc-meeting
minutes available on that page
Documentation on performance of the TPC
NOTE: this was for 2008
These are the TPC hit errors as parameterized by Victor Perevoztchikov in order to normalize pulls (and thus chi squares) of ITTF tracks versus z, dip angle, and crossing angles:
error_xy = sqrt([0]+[1]*((200.-y)/100.)/(cos(x)*cos(x))+[2]*tan(x)*tan(x)) error_z = sqrt([0]+[1]*((200.-y)/100.)*(1.+tan(x)*tan(x))+[2]*tan(x)*tan(x))
where y in the equations is the z coordinate in the TPC, and x in the equations is the crossing angle for error_xy, and the dip angle for error_z. The parameters are:
Inner TPC:
error_xy->SetParameters(0.0004,0.0011513,0.01763); error_z ->SetParameters(0.00093415,0.0051781,0.014985);
Outer TPC:
error_xy->SetParameters(0.0012036,0.0011156,0.063435); error_z ->SetParameters(0.0026171,0.0045678,0.052361);
Plotting these as a function of z and crossing/dip angles gives:
Inner TPC:
Outer TPC:
EPS versions of these images are attached.
As was TPC Hit Errors (2008), hit errors were found for Run 9 by Victor Perevoztchikov.
I created a macro which can be used by anyone to generate these plots, obtainable by CVS checkout from offline/users/genevb/hitErrors.C. Attached to this page are text files used as input for pp500 and pp200 (Victor ran on data with timestamps of 20090326.082803 and 20090425.093105 respectively), and eps versions of these plots.
pp500:
__________________________________
pp200:
-Gene Van Buren
[Update on 2010-06-21: global track momentum resolution has now also been studied using Cosmic rays study, version 2, with some as yet unexplained good performance at very high pT.]
_____________
Jim Thomas has written code to model transverse momentum (pT) and pointing resolution near the primary vertex (DCA) of tracks using various detectors. The code has been tuned to match TPC performance under low luminosity conditions, but assumes (for simplicity) TPC hit errors of 0.06 cm in rφ and 0.15 cm in z (which can be compared with the TPC Hit Errors (2008)), throwing tracks at η = 0.5 and including hits in "nearly all" 45 padrows (padrows 1 and 13 are dropped).
Shown below are the pt resolutions for various options:
Note that the embedding data was shown in Figure 10 of the TPC NIM paper [1]. At low pT, the resolution is dominated by multiple coulomb scattering (MCS) effects. At high pT, the momentum resolution approaches a C * pT2 dependence (note that C can be considered the inverse transverse momentum resolution, as δ(1/pT) = δ(pT) / pT2 for small δ(pT)). For the above curves, C (in units of inverse momentum [c/GeV]) is approximately:
Here is the same model run with only using every other padrow of the TPC:
For the above "less hits" curves, C is approximately 50% higher in all cases:
Additional studies of the momentum resolution come from Yuri Fisyak for Monte Carlo simulations (similar to a thorough embedding study done using TPT in 2002 by Jen Klay) in the following plots for globals and primaries in AuAu200 and pp500 [with pileup] collisions. The comparison is best made with the blue [AuAu globals] and magenta [AuAu primaries] lines above. The data matches reasonably well with the "less hits" model curves, with the exception of an additional offset of about 0.5% for global tracks. The pileup in the pp500 simulation probably causes its results for primaries to have even further degraded resolutions than the red [pp primaries] lines above.
AuAu200 [Run 10 FF setup]:
pp500 [Run 9 RFF setup, with pileup]:
Shown below are the DCA resolutions from the same model described earlier, using tracks with "nearly all" hits, for
[note: I do not know what the dashed lines are]
As can be seen, the field makes only a small impact on the DCA resolution. When using "good" (high quality) tracks for calibrations, I regularly find a mean DCA resolution for global tracks in full field of just under 3 mm.
EPS versions of these images are attached.
References:
1. M. Anderson et al., Nucl. Instr. and Meth. A499 (2003) 659-678