SMD High Voltage Operation

Version 1.10 -- 04/25/06, O.D.Tsai


The SMD detectors are a set of 120 proportional wire chambers located inside the EMC modules (one per module). The operating gas is Ar/CO2(90/10). The nominal operating voltage is +1430 V. As for any other gaseous detector, manipulation with high voltage should be performed with great care.

A detailed description of the system is given in the Appendix.

SMD HV must be turned OFF before magnet ramp !
Standard Operation includes three steps.

Turn HV ON
Log Defective Modules

To turn SMD HV ON the procedure is:
  1. On HOOSIER.STARP.BNL.GOV computer double click on the SMDHV icon on the Windows desktop.  The 'SMD HIGH VOLTAGE CONTROL' window will open.
  2. On the SMD HIGH VOLTAGE CONTROL window click 'POWER' button.
    1. 'POWER' button will turn RED
    2. In no later than 90 + 150 + 300 sec in window 'Current Mode' you will see the message - "Physics Mode"
    3. All modules with high voltage on them will be shown in GREEN, LIGHT BROWN or YELLOW.

To turn HV OFF on SMD the procedure is:
  1. Click on the green 'POWER' button.  Result:
    1. 'POWER' button will turn from green to BROWN
    2. after a 30 sec. or so small window will pop-up telling you that voltages an all channels reached zero.
  2. Click 'OK' on that small window to stop the program.

To Log Defective Modules

  1. Scroll down the window -- you will see three tables
  2. Log contents of the left table called 'Defect Module List' if any modules are presented here.
  3. Log contents of the right table called 'Modules tripped during Standby' (for example Run XXX  #8 - 3 trips, Run XXX  #54 - 1 trip)
  4. Close the 'SMD HIGH VOLTAGE CONTROL' window.
Detailed description of the SMD HV Program and associated hardware settings can be found in Appendix.

Indicators to watch:

1.  Interlock went RED

In case STAR global interlock went ON
  1. Interlock led will turn in RED
  2. the SMD HV program will turn OFF HV on all SMD channels and program will halt.
  3. Operator should close SMD HV Voltage control window.
Once STAR global interlock will be cleared follow usual procedure to power up SMD.

 2. Server Timeout went RED or SMD HV Control program is frozen.

This is an unusual situation and SMD Expert Contacts should be alerted.  The lost communication to SY1527 should not lead to immediate damages to the SMD chambers.

In case communication to the SY1527 is lost for some reason the 'SERVER TIMEOUT' led will turn RED.  In case SMD HV Control program is frozen the 'Current Time' will not be updated.

Procedure to resolve problem is:
  1. Open terminal window on EMC01.STARP.BNL.GOV (monitor is on top of SMD HV Control PC)
  2. ping -- observe that packets transmitted and received.
    1. If there are no communication with SY1527 (packets lost) -- Call one of the Expert Contacts!
  3. If communication is OK, then stop ping and type telnet 1527  -- You should see 'login window for CAEN SY1527 system'
  4. Press any key
  5. Login as 'admin' with password 'admin' -- you will see Main Menu window for SY1527
  6. From 'Main' chose 'Channels' by pressing 'Enter' -- you will see Channels menu window
  7. Verify HV is presented on channels (VMon)

Usually second terminal window is open on HOOSIER.STARP.BNL.GOV to monitor SY1527 HV power supply. If this window is not open use “putty” and open SY1527 session.

Now you can operate HV using this window, but if there is no emergency to turn HV OFF you should first try to restart SMD HV Control program.  

Basic operations from that window are:
Turn HV ON             

  1. press Tab key
  2. scroll to 'Groups' menu
  3. press 'Enter' to chose "Group Mode" --you will see highlighted column
  4. scroll to "Pw"
  5. press space bar -- you will see "Pw" will switched from On to Off and VMon will start to decrease.
Turn HV ON
  1. press Tab key
  2. select 'Group' mode
  3. scroll to IOSet
  4. type 5.0  (Current limit 5uA)
  5. scroll to Trip
  6. type 0.5 sec
  7. Verify that V0Set is 1430 V
  8. Scroll to Pw
  9. press Space bar -- you will see Pw will switch from OFF to ON and Status goes to Up.  VMon will start to increase.
Once HV will reach to nominal it is very important to switch I0Set to 1.6 uA and Trip to 0.1s on all channels.  Some channels might trip after I0Set and Trip were changed, that is 'normal'. For those channels I0Set and Trip should be set to 5 uA and 0.5s. To do that:
  1. Press Tab key
  2. reselect 'Group' mode
  3. Change I0Set and Trip for tripped channels
  4. Power them up - scroll to Pw, and press Space bar.
Usually it is safe to keep channels in 'Group' mode to be able to switch them OFF fast in case of emergency.


Before you start:
"Be afraid, even paranoid, and that gives you a chance to catch bad effects in the early stages when they still do not matter" 
--J. Va'vra (Wire Aging Conference)

Detailed information regarding SY1527 mainframe and A1733 HV distribution boards can be found at CAEN web page.

The SMD HV is supplied by the CAEN SY1527 HV system.  The mainframe is located in rack 2C5 (Second Floor, Third Row, near the center).  The HV cables run from modules to the SMD crates (15 cables per each crate).  At each crate HV cables re-grounded on patch panels assuring same ground for HV and signals to be read. From SMD crates, the HV lines then run to the SY1527 system. There are 10 HV cards, 12 HV channels each (model A1733) inside the mainframe to supply high voltages to the SMD chambers.  The parameters of the high voltage system controlled via Ethernet.  The GUI based on LabView and CAEN OPC server.

Hardware settings are:

 HV Hardware limit set to +1500 V on each of A1733 cards.
 HV Software limit (SVMax) set to +1450 V for each channel.
 Communications settings for SY1527 are:
Net Mask
User name Admin
Password Admin
Position of switches and status of LEDs on the front panel of SY1527
(from top to bottom, HV is Off)
Chk Pass                     On
Toggle Switch 'Loc enable'   On
Ch Status     'NIM'          On
Interlock     'Open'
Master                       On
+48 V                        On
+5  V                        On
+12 V                        On
-12 V                        On
Main                         On

Each A1733 card should have 50 Ohm Lemo 00 terminator to enable HV.

Description of SMD High Voltage Control program.

All SMD HV software is installed on EMCSC.STARP.BNL.GOV in folder C:/SY1527

The SMD HV Control provides one button operation of the HV system for the SMD. There are three main functions Power On, Physics Mode, Power Off. There are two configuration files Conf.txt and Conf2.txt which defines ramp up speed and trip settings for different mode of operation.

The nominal settings for Power On are (C:/SY1527/Conf.txt):

V0          1430 V
I0Set       5 uA
Trip        0.5 s
Ramp Down   50 V/sec
Ramp Up     20 V/sec

All channels are allowed to be ramp up in three consecutive attempts. If the first attempt (90 sec) for given channel lead to trip then ramp up speed will be set to 10 V/sec and second attempt (150 sec) will be performed. If second attempt will lead to trip then ramp up speed will be set to 7 V/sec and third attempt (300 sec) will be made. If all three attempt led to trip the program disconnect that particular channel from HV (corresponding led on main panel will turn in RED).

In no later then 90 + 150 + 300 seconds program will change parameters of I0Set and Trip form 5 uA and 0.5 sec to 1.6 uA and 0.1 sec and will switch to the Physics Mode.

The nominal settings for Physics Mode are (C:/SY1527/Conf2.txt)
V0          1430 V
I0Set       1.6 uA
Trip        0.1 s
Ramp Down   50 V/sec
Ramp Up     20 V/sec

Channels allowed to trip no more then 6 times during the Physics Mode. If channel will trip then I0Set and Trip for that particular channel will be set to 5 uA and 0.5 sec and program will try to bring that channel up. On front panel Alarm Status will turn in RED, corresponded message will pop up in 'Current Mode' window, and corresponded to that channel LED will turn in YELLOW or RED.  Once voltage reach 90% of nominal all indicators will turn to normal status.  Usually it takes about 15 seconds to bring channel back to normal.  At the bottom of the screen the right table with modules that tripped during the Physics Mode will be updated.  If some channel will trip more than 6 times that channel will be HV disabled by the program and corresponded led will turn RED.  The left table on the bottom of the screen will be updated.  Such cases should be treated by experts only later on.

All SMD channels during the Physics Mode is under the monitoring.  Each 3 seconds or so, the values of Voltage, Current and time are logged in files XX_YY_ZZ_P.txt in C:/SY1527/Log, where XX - current month, YY - current day, ZZ - current year, and P is V for Voltages and I for Currents. The current time saved in seconds.  The macro C:/SY1527/smdhv.C plots bad channels history and fills histograms for all other channels.
Turn Off is trivial and no need explanations.

The meaning of the LED on main panel are:
Green – channel is at nominal HV, current < 1 uA
Brown – channel is at nominal HV, 1 uA < current < 5 uA
Yellow – the HV is < 50% of nominal
Red    - channel was disconnected due trips during ramp up or physics modes.
Black  - channel disabled by user (Conf.txt, Conf2.txt)

It is important to monitor channels with high current (“Brown”), as well as channels that shows high number of trips during the operation.  Note: some channels (54 for example) probably has a leakage on external HV distribution board and believed to be OK in terms of discharges on anode wires as was verified during summer shutdown. The other might develop sparking during the run or might have intermittent problems (#8 for example). If problems with sparking will be detected at early stages then those channels might be cured by experts during the run, without of loss of entire chamber as it was happened during the first two years of operation.  

The C:/SY1527/ allows to monitor single channel. You may overwrite nominal parameters of HV for any channel using that program (it is not desired to do that). This program can run in parallel with the Main SMD HV Control program.  The operation is trivial, specify 'Channel to monitor' and click on 'Update Channel'. If you wish to overwrite some parameters (see above) then fill properly VOSet etc. icons and click on Update Write.

Important! Known bug.
Before you start you better to fill all parameters, if you do not do that and stop the program later on the parameters will be overwritten with whatever it was in those windows, i.e. if V0Set was 0 then you will power Off the channel.  

 In some cases it is easy to monitor channels by looking at front panel of the SY1527 mainframe. The image of this panel can be
 obtained by opening telnet session (telnet 1527) on EMC01.STARP.BNL.GOV.

 All three programs can run in parallel.

 -----Experts to be called day or night no matter what---

 1. The operation crew lost communication with SY1527
 2. Any accidental cases (large number (>5) of SMD channels
    suddenly disconnected from HV during the run)

For experts only!

What to do with bad modules?

1.    If anode wire were found broken then disable channel by changing 1430 to 0 in both configuration files. That should help to avoid confusions of detector operators.

2.    If anode wires are OK, and module trips frequently during first half an hour after power Up then it is advised to set HV on that particular channel to lower value (-100V, -200V from nominal etc…) and observe the behavior of the chamber ( In some cases after a few hours module can be bring back to normal operation.

3.    If step 2 did not help, then wait till scheduled access and try to cure chamber by applying reverse polarity HV. Important, you can do that using good HV power supply (fast trip protection, with current limit 5uA), or by using something like ‘Bertran’ with external microammeter and balance resistor of no less then 10 MOhm, only! In any case you need to observe the current while gradually increase HV. In no case ‘Bertarn’ like power supply might be left unattended during the cure procedure. It is not advised to apply more then -1000 V. In some cases curing procedure might be fast (one hour or so). In others it might take much longer (24 hours and more) to bring module back to operation. In any case I would request to talk with me.

4.    The SMDHV is also installed on EMCSC.STARP.BNL.GOV and can be run from there, although that will for sure affect BTOW HV, be advised.

  Version 1.00 was written 11/12/03
  Version 1.10 corrected   04/25/06

A copy of this manual as a Word document is available for download below.