1 status of the calorimeter pmt’s time alignment lhcb calo meeting 4.09.07 anatoli konoplyannikov...

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Status of the calorimeter PMT’s time alignment

LHCb CALO meeting 4.09.07 Anatoli Konoplyannikov /ITEP/

Introduction

Development status of the PMT time alignment procedure

Hardware outline PVSS control software for performing the scan data collection with LEDTSB board Detector signals relative time alignment algorithm and first test with HCAL C side electronics Scan test analysis software and first result of the time alignment with LED control system

Conclusion & Planning

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Introduction

At the moment the installation of the CALO sub-detectors with own electronics is near finish and the next important commissioning task is the calorimeter sub-detectors inter-channel relative time alignment. About one year ago we decided to use the LED system to perform this time alignment. The offered method is based on the analysis of the collection of the time scanned data (The method description is attached in the backup slides). The scan data could be obtained with using the main DAQ or with the “spy DAQ” implemented by LAL group in CROC_v2 board. In my opinion, at the moment to do these scan tests with main DAQ is difficult. An autonomous “spy” DAQ mode is more convenient for the sub-detectors commissioning. A half year ago the first version of the software tools to perform a scan data collection with one FE board have been developed and tested. During the last time the soft was extended for one FE crate scan data collection and first measurements have been done for HCAL side C sub-detector. (All scanned data are available. See CALO logbook.)

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Calorimeters LED control

LHCb week meeting 4.09.07 Anatoli Konoplyannikov

LEDTSB CROC FEBs

TTCrxSPECSslave

Bchannel

CLK

PIN withAmplifier PMT

LED

8

Front-End Crate

Time alignmentcircuits

1

2

3

4

5

6 Inner

MiddleOuter

Using Hardware:

1. HCAL FE crates 22 and 23 with FE boards, CROC_v2 and LEDTSB board.

2. 52 LED drivers with PIN diode and amplifier controlled by HV_LED_DAC board and configured by ECS based on the lbCaloHv component.

Developed tools:

Software for PMT HV and LED intensity control.

Software for data collection in “spy mode” that is initialized from ECS control panel for readout of the FE boards by CAT TimingScan process.

Data analysis program for calculation the needed delay settings for FE boards.

HV_LED_DAC

SPECS

SPECSStatus of the PMT time alignment procedure development

Sketch of the signals flow in ECAL/HCAL sub-detectors

4LHCb CALO meeting 4.09.07 Anatoli Konoplyannikov /ITEP/

Calorimeters LED controlDetector signals relative time alignment algorithm and first realization

Online run control panel for making delay scan.

What was improved:

DIM interface PVSS to CAT (CAT Server) and TimeScan process (initially developed by Frederic) were re-optimized for working with one FE crate. Then a dedicated panel for making delay scan has been designed.

The main features of the timing scan tool are following:

• The main variable is a LEDTSB channel and a timing scan in selected time range and step is doing for this channel.

• The tool is directly connected to CALO database and readout is performed only for FE boards with FE channels illuminating a current LED.

• Format of the output data is a text sequence of a mean ADC value and RMS.

Software tool for data collection in “spy mode”

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Calorimeters LED control show the online analysis steps;

produce the root files with many histograms those show the amplitude and time behavior of the individual channel and FE crate summary;

generate an output log file with detailed information about problematic channels;

produce the time values for FE delay chips setting;

calculate the fit parameters of the PMT delay versus HV dependence for all channels.

Signal shape analysis algorithm:

1. normalization the raw signal shapes of the PMT and PIN on max value;

2. fit a signal leading edge, calculate the derivative, fit it and finally get the signal arriving time on the level of 50%.

3. normalization of a PMT arriving time on PIN time for excluding delay differences of triggering cable and LED driver.The developed tool is based

on the CERN ROOT package.

Time (ns)

Data analysis tool allows :

50 %


Calorimeters LED control

Test conditions: HV = 1050 V, LED = 1700 cnt, ADC sampling time is 5 ns.

First of all the stability test and comparison of the HCAL LED1 – LED2 data have been done for checking the behavior of the procedure.

Stability measurement of the signal arriving time for two sets of Scan test, were done with two days interval and result is shown on the histogram. X axis of the histogram is a time difference T_second – T_first for all channels.

In HCAL case it is easy to make a comparison of the delay measurement for each PM by two LED’s.

The main impact in the distribution width is a PIN cable length difference.

Analysis results

Time (ns)Time (ns)

N N

From the beginning it was found that 3 channels in crate 22 have a problem.


Calorimeters LED controlFirst result of the time alignment with LED control system

Test conditions: HV = 1000 V, LED = 1700 cnts, FE ADC’s sampling time was 5 ns.

Signal arriving time distribution for HCAL crate 22

Scope measurement and Scan data analysis results comparison.

Measured time variation is matched with the Rustem’s scope measurements. The time range measured by scope is from 0.8 to 5.3 ns for HCAL side C.

Analysis results This distribution of the times those will be put after an additional correction on HV value and detector cell radius into the FE Delay chips.

As one can see, if we exclude 3 bad operating channels, the min – max range is about +- 1.5 ns.

Time (ns)

N


Calorimeters LED controlFirst result of the time alignment with LED control system

PMT HV scans have been done for seven HV values

Plots of the dependences of a PMT delay versus HV for one LED illuminating 16 channel of HCAL module 25.

Test conditions: HV = 850 - 1150 V, LED = 1700 cnts, FE ADC sampling time is 5 ns.

Analysis results

Histogram of the linear fit paramete[1] of the PMT delay versus HV dependences for all PMT’s of crate 22.

NTime (ns)

HV (V) Par[1] (ns/100V)

9LHCb week meeting 4.09.2007 Anatoli Konoplyannikov

Conclusion & Planning

First release of the software tools for making relative time alignment for an unit of one ECAL/HCAL FE crate have been developed.

The procedure of the relative time alignment was tested with HCAL side C electronics and the result seems optimistic.

Obtained scan data allows to get a various information about detector and electronics status.

Next steps: Optimize a time of the scan data collection; Develop an user friendly GUI interface for non expert operation; Optimize the tool for working with ECAL data base; If it is interesting, help to adopt this tool for PS/SPD sub-detectors; Improve the LEDTSB calibration program. If CROC_v5 will have the same “spy DAQ” feature as v2, update the tool for working with many crates synchronized with main LHCb TFC system. When the ECS Scan template of the calibration run with main DAQ will be available, adopt the tool for working in new environment.


End of Main. See Backups

10LHCb week meeting 7.03.06 Anatoli Konoplyannikov

Case when the LED triggering cables are different, clear fibers in each group are different too but with the same length in the group (ECAL).

1. Set all FE Delay Chips in the middle of range (12 ns). It means to fix an ADC sampling time.

2. Collect ADC data of PMTs and PIN diodes incrementing delay of the LED triggering pulse by 1 ns in a needed range for each PMT group fired by one LED.

3. Analyze the collected data and calculate the needed delay values for Delay chips, taken into account a mean HV value into the group, difference of clear fiber length and a particle time of flight versus an angle distribution.

4. Set correct values to all FE Delay Chips.

Two possibility of the time normalization:

•measure the cable length;

•use PIN diode response.

Timing diagrams of the raw and analyzed scanning data

LED delay time (ns) time (ns)

~ 4 ns PIN PMTs

Outer Group

Inner Group

Time adjustedon PIN

Set to DelayChip

Normalization Timeon middle group

Raw data

Method descriptionBackup

Calorimeter detectors relative time alignment.

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Calorimeter detectors relative time alignment.


One year ago two methods (“strategies”) of the calorimeter time alignment with using LED system were presented. One for HCAL (Rustem + Yuri) is based on the direct measurements by the scope and second one for ECAL is based on relative time measurements by FE boards and LEDTSB.The relative time alignment method is based on the three main assumptions:For a given HV value, a PMT transition time is the same for all our tubes (HM R7899-20).The clear fiber length is the same (or well known from production data base) for each PMT group (9 and 16 PMT’s) illuminated by one LED.There is a hardware tool allowing to measure a PMT signal arrival time simultaneously for all tubes in a PMT group. (LEDTSB board varying a LED flashing time with 1 ns step in range unto 300 ns). In reality all above mentioned assumptions have an error:A given HV value is produced by CW base with precession of 1%, then the precession of the DAC IC’s reference voltage of the HV_LED_DAC boards is about 1% too. An estimated PMT transition time spread is about +- 0.05 ns.The clear fiber length is well known (let say) with precession +- 2.5 cm that leads to a time precession of about +- 0.15 ns. (ECAL clear fiber light transmission delay is 5.9 ns/m [see Kirill’s report]).The precession of the PMT signal arrival time measurement is about +- 0.15 ns. (Measurement result was presented on the last commissioning meeting).

BackupMethod description


From first two assumptions one can conclude that using this method we can find the signal cable delay time spread that needed for the physics run time delay adjustment.An estimation of the signal cable delay time spread (for about 6000 ECAL cables) we can do taken into account the following:Cable transmission time dispersion due to a cable quality. For the using cable the delay dispersion is about 2%, which leads to about +- 1 ns time spread of 20 m cable length. Precision of the cable cut at production time is about +- 10 cm -> +- 0.5 ns.Connectors repairing and cable cutting leads to – 0.2 ns.On base of the first assumption one can assume that the mean values of the signal time distributions for each PMT group must be the same. The error of this statement is RMScable_delay / (N_PM_in_group)^0.5. Taken into account all mentioned above the estimation of the total error of the ECAL relative time alignment is about +- 0.5 ns.Possible scenario of the ECAL relative time alignment for physics is:

Set a needed (optimized for ECAL region, but not below of 10K of PMT gain) HV value the same for all PMT’s in a studied group.Make a LED delay scan for the group and analyze the channels with a significant time difference from a mean value. (may be using scope)Apply all calculated (or estimated from MC) coefficients to a formula using a fit of the many time measured the PM delay vs HV curve and calculate a needed settings for FE delay chips.

For the PMT gain monitoring with LED and PIN we do not need to do anything (measure cable, fiber lengths …). One can set all needed HV and LED intensity values then make a delay scan by LEDTSB, calculate data and set the correct delay values to LEDTSB.

Calorimeter detectors relative time alignment ( continued ).

BackupMethod description



BackupAnalysis results

Total PIN information




Total PMT information of crate 22




PMT signal charge versus HV for the HCAL tubes of Module 25




Log file of the analysis results for HCAL crate 22

1 status of the calorimeter pmt’s time alignment lhcb calo meeting 4.09.07 anatoli konoplyannikov...

Documents

time scanned data

fe crate scan data collection

fe boards

delay scan

led system

scan tests

output data

calo subdetectors