E907 TPC Electronics
Anode Notes

LeCroy 1440 Documents
hv_control 1440 Control Software
Anode Cable Map
Calibrations
Ramping

LeCroy 1440 Documents

Documention for generic LeCroy 1440 Systems

Fermilab PREP LeCroy 1444 Page
1444 Operating Manual
System Calibration Manual

Special Features of 1444 Cards, and Modifications

Meanings of Pseudo-Channels

The 1444 cards, when used with v1.7 firmware, use some pseudo-channels for special purposes:

1444 Card Channel Functions
Channel Function and Sensitivity
0-7 Output voltage, 2 V/count
8 Ramp rate.

0 counts = 300 V/s
4096 counts = 1500 V/s

The actual ramp rate will vary about ten percent from channel to channel.
9 Sets/resets the trip system for the card.

Writing a 0 disables trips, resetting tripped channels to the demand voltage.
Writing 2048 enables the trip system.
10 Not used.
11 Sets the DC current limit for all channels on the card.

The normal sensitivity is 1 µA/count, 1024 µA full scale.
12-15 Set the AC trip limit for pairs of channels (12 controls 0 and 1, etc.) Larger values provide lower sensitivity.

Note that hv_control

High Current Sensitivity

Our 1444 cards are modified for high current sensitivity. From the E895 Logbook:

Note on currents in 1440 HV:

Monitor & trip current levels are normally read out in muA. However, we are now using modified 1440P cards which monitor currents with 100 times normal sensitivity, and trip with 50 times normal sensitivity.

Modified cards can be recognized by either MOD 300 or MOD 100 on the top or bottom of the panel where the SHV connectors are located.

We have checked this with our calibration procedure, see the Calibrations section, below.

hv_control 1440 Control Software

The control program for the 1440 crates is called hv_control. This is usually run as user daq on e907hv. The program hv_control has to be run from its parent directory, ~/hv_control/ to find its various configuration files.

The TPC 1444 cards are in slots 12-14. (Card 14 is the spare.)

The relevant configuration files are

hv_control Configuration Files
File Parameters
channel_names.config String name for each HV channel.
highvoltage_cards.config Type of card in each 1440 slot.
standard.hv Standard settings for each channel:
voltage
backup voltage (not used on 1444 cards)
trip limit
voltage_limits.hv Control settings for each channel:
voltage limit
channel polarity
detector group
under voltage threshold
over voltage threshold
critical under voltage threshold
critical over voltage threshold
trip threshold
default ramp rate
maximum ramp rate
tpc_param.hv Special 1444 parameter settings for TPC Anode cards. This file gives the default values for the
ramp rate
DC current trip
AC current trip
hv_control Documentation

Anode Cable Map

Anode Cable Map
Anode Cable LeCroy 1440 HV Supply
Slot Channel
0 BA-V-083 12 0
1 BA-V-088 12 1
2 BA-V-086 12 2
3 BA-V-085 12 3
4 BA-V-093 12 4
5 BA-V-096 12 5
6 BA-V-092 12 6
7 BA-V-095 12 7
8 BA-V-094 13 0
9 BA-V-091 13 1
10 BA-V-090 13 2
11 2 13 3
12 6 13 4
13 3 13 5
14 1 13 6
15 5 13 7
spare 4 (may be bad)
spare BA-V-081
spare BA-V-082
spare BA-V-087
spare BA-V-089
spare BA-V-084

Calibrations

The anode power supply channels were calibrated on 3/5/04 and 4/14/04. The raw measurements and analysis are in Anode Calibrations.xls.

Each section below describes the calibration steps and results.

Voltage limit Hardware voltage limit for each channel.
Output calibration Voltage and current calibration.
Current trip Current limit trip setting.

Voltage Limit

The 1444 cards ignore the 1440 front panel global voltage limit dial settings. Instead, each 1444 channel has a hardware voltage limit, set by adjusting a potentiometer on the rear panel. The corresponding limit voltage is available on the monitoring header. All channels were set to ~1350 V or less.

After the adjustment on 4/14/04 the average limit was 1343 ±14 V (1 sigma).

The exact values for each channel were

Hardware Voltage Limit Setpoint for Each Channel
Slot Channel Voltage Limit
12 0 1333
12 1 1340
12 2 1342
12 3 1337
12 4 1346
12 5 1347
12 6 1353
12 7 1342
13 0 1345
13 1 1345
13 2 1344
13 3 1340
13 4 1345
13 5 1360
13 6 1357
13 7 1349
14 0 1345
14 1 1353
14 2 1337
14 3 1343
14 4 1343
14 5 1366
14 6 1346
14 7 1345

Output Calibration

Voltage and Current Measurement

Output voltage was calibrated using the UVA Fluke multimeter. The output voltage was set to 0, 400, and 900 V. We recorded the readback voltage, the voltage on the rear panel monitor header, and the actual output voltage, all with no load.

We used a known load resistor to measure the current. Sten Hansen measured the load resistance as 816 Ω ±1%. We recorded the readback current and the current monitor voltage on the rear panel monitor header. For some number of channels we verified that the voltage under load was the same as under no load. From the real voltage and the load resistance we calculated the real current.

Analysis

For each channel, we calculated linear fits using the data from the three setpoint voltages, 0, 400, and 900 V. The fitting functions are shown in the following table. We then compared the resulting parameters for each channel, and found that all channels can be fit together with a single set of parameters, also shown in the table. This is to be expected, since all the functions use one of the readback values, which are all measured by the single ADC in the 1440 controller. Essentially, we are calibrating this ADC.

Calibration Functions, Fit Parameters, and Errors
Function Parameter
a ± σ b ± σ
VSET = a × VREAL + b 0.9700 ± 0.0017 0.9 ± 1.0 V
VREAL = a × VREAD + b 1.0271 ± 0.0016 -4.7 ± 0.9 V
IREAL = a × IREAD + b 5.1878 ± 0.0075 nA/count -1.5 ± 1.0 nA

Note that we quote VSET and VREAD in volts. The 1444 cards use 2 data counts/V for these numbers; this is handled by the hv_control software, by taking the input number and dividing by two, to get the data count to write to the 1444.

We quote IREAD in data counts, hence the units on the current slope coefficient.

Finally, note that the constant coefficients are consistent with zero. When working at low voltage, it is probably necessary to use the individual channel calibrations, rather than the global average.

Current Trip

We want to set the DC current trip limit at 500 µA, which corresponds to 400 V measurement on the calibrated load resistor. We set the output to 400 V, then decreased the trip limit setting until the channel tripped. We computed the trip sensitivity as IREAL⁄(ILIM + ½) in nA/count. These turn out to be uniform across channels, but not across cards.

The resulting calibrations, as nA/count, VSET/nA, VSET/0.5 µA, and ILIM display, are shown in this table.

DC Current Limit Sensitivity and Trip Settings
Card 12 13 14
ILIM Sensitivity (nA/count) 6.88 2.52 4.94
"VSET" Sensitivity (V/nA) 0.291 0.793 0.405
"VSET" for 500 nA 145 397 202
hv_control Display Value (counts)  73 198 101

Ramping

hv_control supports ramping individual channels (up to voltage: ^R; down to zero: ^W) and whole cards (up to voltage: ^K; down to zero: ^P). When ramping up, the hv_control asks for the set voltage and the step size. Usually we ramp to 1300 V in 50 V steps.

The current version (3.1.1) of hv_control ramps one channel at a time. If we go immediately to full voltage in one ramp cycle, we will end up with the full voltage between adjacent anode channels, which seems a little harsh, so we usually ramp everbody in stages: 20 V, 500 V, 1000 V, 1300 V. (There seems to be a bug when the anodes start at zero, with the result that only small initial steps, e.g.20 V, work.)

Valid XHTML 1.0! PDB, 6/22/04