PHOS data taking status - lessons learned/implications for EMCAL

Outline

Recent work in PHOS lab @ CERN, May and June 2007 (PHOS & EMCAL team; Josh, Lamia, Sasha V, Hans, DS et al)

• LED/Pulser data; calibrations & dead channels

• Cosmics data; track candidates

• Misc. points: signal fitting, zero suppression, configuration database

1 Module PHOS

• 112 FEE Cards• 8 TRU• 4 RCU• 3584 input

channels• 7168 readout

channels 10 bit

56

64 crystals (one 20 degree sector)

14 FEEcards in1 TRU domain

PHOS module Nr.2 placed in the z plane. The crystal counting (i,j) is shown relative to the x-z coordinate of the Interaction point

16

28

x (towards center of LHC )

z (Bea mli ne direct ion Belle garde)

(0,0) i=0..63

j=0..55

RCUpartition(1 of 4)

projection ofinteraction point

PHOS module( 3584)

partition(1 of 4)

C.f. : one EMCAL SM has 24*12*4 = 1152 towers, and thus 2304 readout channels.

PHOS aujourd’hui

Will soon be closed up, rotated,and cooled down..

Cosmics taken to date have been at room temperature,and with the crystals oriented in the horizontal direction.

Online / PHOS labHave recently switched to DATE6 (latest and greatest) + installing of TRUs, busybox etc.

Nice setup with help from DAQ crew – using DAQ logbook, writing data directly into ROOT format etc.

DeadMap Channels from LED run 7261 [Lamia; earlier hardware fixes by Sasha V.]

42 Dead Channels ~ 1 %[high gain only]

Some flakiness observed;Intermittent problem channelscome and go.- Frequency should be evaluated.[Lamia et al have taken many LED runs to study this]

Relative Calibration

With a constant LED pulse signal, we do scans of the average signal amplitude vsAPD bias HV setting. The HV setting is done via DAC register on the Front-End cards.

We fit the gain curve of amplitude vs HV, or DAC value, for each channel.Similar studies were done for the EMCAL testbeam at FNAL.

- We can do a first/rough gain balancing between different towers (assuming LED signals do not vary too much tower-by-tower) by selecting a reference amplitude and dial in the corresponding DAC values for each channel. [Software by Josh.]

Before

After

Cosmic Track:

Tmp. dead FEE card

Cosmic Track (lego)

Another Cosmic Event

Standard fit (gammaN) to the ADC values vs time.

Fit parameters are Pedestal, Amplitude,Tau, and Tmax.

Misc. points for EMCAL:

Sensitivity of tau value to fit parameters

Since the shape changes in the tail, we wanted to see if the tau value changed as a function of where we stop the fit. The cut we use, is to stop when the ADC value has reached a certain fraction f of the maximum ADC. [I.e. a fraction cut value of 0.6 means that we stop at 60% of the peak height.]

We then noticed that the obtained tau values varied quite a lot depending on where exactly this cut was made, when we used the default order of the gamma function, gammaN = 2.If the function we fit with had the correct shape, one would not expect a large variation as a function of where we stop the fitting..

A plot of the cut dependence for the average extracted tau value, for different gammaN settings, is next.

http://dsilverm.web.cern.ch/dsilverm/phoslab/taucutdep.gif

True shape seems to be more like gammaN ~= 1.8. Will need to test for EMCAL shaper later..

Cosmic Runs & Calibration:Cosmics with properly oriented and cooled-down PHOS in a few weeks should be more interesting. We should be able to see MIPs/same energy peak over the whole module.

Purpose of calibration is to set all channels to the same relative gain.With pulser runs this is limited by variation of LED light for different towers. *We probably want the LEDs and FEEs to travel along with the SMs for the cosmic etc tests and calibrations before the installation..

*With cosmics and testbeam, one also wants the LED that will be used in data taking so that one can establish the relation between LED peak, and the energy scale in GeV.

*For the testbeam in the fall we should probably try to take some cosmics also to check the agreement between a cosmic balancing and balancing with beam.Should also make sure that the files can be processed offline with AliRoot etc.

With physics data, later on, one has access to the following means: MIPs (good statistics), pi0’s (2 gamma) and electrons (E/p requirement).

Missing 1 out of 64 channels..

Still missing first low gainchannel 0, chip 2 on everyFEC..

Will try the trick from ZhongBao (activate non-existing chip 1) to see if this can be cured..

Zero suppression registers Several possibilities and options for ALTRO zero suppression. We have mainly used the automatic/variable zero-suppression mode. [Thanks to R. Bramm (TPC) for advice.]

Zero Suppression problem

Some problems so far on zero suppression front..:

1) We have a small error frequency (~0.1-0.5%, depends on thr etc), where the channel trailer info and the number of data samples does not seem to match.

A feature(?) when using ROOT raw data format is that these errors are not seen then – just a caution that the underlying problem is probably still there though..

2) We don’t use the ZS mode we should be using, with a fixed pedestal that

doesn’t change automatically – should perhaps not be too hard to change that.

Check: Matching of automated (VFPED)

and fitted pedestal (signal run)

All channels,

Low gain

and

High gain.

Online monitoring Plan:

New data-quality-framework for online monitoring from DAQ group (Filimon) called AMORE is expected to have first release in July.

Summer student from Jyvaskyla (Timo) is at CERN for two months, and I have suggested that we could turn EMCAL and PHOS unofficial testbeam/online analysis tools into something more official and acceptable..

DCS: DB Configuration Info• FEE Configuration a la baseline settings, zero

suppression registers, thresholds etc. not yet fully implemented for PHOS, so database development for that is somewhat premature at the moment.

• APD configurations (HV bias settings) however do exist (few hundred different ones), and provide a good (relatively simple) test case for DB infrastructure etc.

• I think I can handle the DB end for EMCAL, but we probably need someone (Creighton?) to help/handle the step between PVSS and DCS; FED and feeServers. May be already part of the plan, otherwise - volunteeers would be most welcomed.

Summary• Currently an active time for PHOS commissioning/tests (installation

in about 5 weeks). EMCAL folks are participating/helping out.

• A lot of similarities between PHOS and EMCAL, especially on electronics side; many things of common interest and benefit.

We have a good opportunity to work together, and learn what to do, or not to do, for EMCAL.

• I hope to have a more clear idea of what should be done on online fronts (monitoring, calibration, online detector algorithms etc) by this fall. Testbeam + collected data there should be an important exercise.

Terry (+ DS) will be at CERN from Sep 2007 to Sep 2008.