calib review

Slide1: 

May 13, 2003 Renee Fatemi EEMC Calibration and Commissioning Summary

Calibration Procedure Overview: 

Collect data on tower response to MIPs while EEMC is in horizontal position Characterize tower response to 300 mCi Co-60 source scans Correlate and parameterize the relationship between the tower response to MIPs and source scans IV. Once detector is fully installed and fibered to PMT’s in WAH, perform source scan on each tower and adjust PMT high voltages in order to place MIP peak in desired position. Calibration Procedure Overview

ENDCAP test structure IUCF: 

ENDCAP test structure IUCF One 30o sector of megatile layers 3-9, 2 SMD layers and one plastic spacer layer were interleved with radiators 1-9. Megatile layers 10-23 rested in plywood “radiators” which simulated the geometry of the fully assembled detector.

MIP Calibration at IUCF: 

A cosmic ray test stand, consisting of 2 trigger paddles and 2 sets of x-y wire chambers, was constructed in order to track MIPs through the towers and SMD layers of the EEMC. MIP spectra were collected for each tower in the test structure. The centroid of the MIP peak and the voltage settings of the tubes were recorded. ADC channel MIP Calibration at IUCF Tower 8 MIP peak

Source Scans at IUCF: 

Source Scans at IUCF time Tower 8 ADC Radial grooves were machined in the spacer layer for every 6o sub sector. The 300 mCi Co-60 g-ray source was slowly extracted at a constant rate – allowing every tower and SMD strip to be illuminated. The effect of the source passing by the tower is easily discernable above the dark current. Source scans were performed on sub sectors A,B,D,E for all possible spacer layer configurations.

Source Scan Analysis: 

S(ADC-ped)*bin time Maximum of Weighted Sum / MIP Centroid Tower # - 6 Source Scan Analysis The weighted sum of the source ADC spectrum above pedestal is highly peaked in time. The maximum of this peak is strongly correlated with the corresponding MIP centroid for a given tower.

Source Scans in the WAH: 

Source Scans in the WAH Calculate final MIP peak position as a function of h – defined by setting the highest channel of FEE 12 bit ADC equal to the energy deposited by a 60 GeV pT photon in one tower. Perform source scan when detector is mounted on the pole tip. Calculate MIP ADC channel for initial PMT voltage setting. Calculate and set new PMT voltage in order to reposition MIP centroid. IV. Repeat scans until calculated MIP peak is positioned in the correct channel

Calibration Status before Collisions: 

Completed 1 iteration of source scan procedure for 144/240 installed PMTs. Performed 3 iterations of source scan procedure for 24/240 installed PMTs. 1st pass calibration of 70% of tubes completed before collisions at STAR Source scans used in conjunction with LED and Laser tests to diagnose problems with cables, connectors and dead tubes. Currently 5% of channels/tubes are non-functional. Calibration Status before Collisions

Calibration with Beam & LEDs: 

The yellow and blue spectra show a typical raw and isolated tower ADC response to minbias pp collisions. The slope of the blue spectra is inversely proportional to the gain of the tube. The average slopes of tubes with optimum source scans are used to define the ideal h dependence, shown by the black lines. The gains of the remaining tubes are moved toward the average. The average slope for all tubes in one hbin is given by the magenta line. Calibration with Beam & LEDs ADC ch Tower #

Calibration Continues…: 

Calibration Continues… Current Status: Average gain in h is fine but spread in f ~ 20%. LED runs during longitudinal commissioning could improve this. Gains are uniform enough to be included in the trigger. Goals for remaining 2/3 of ENDCAP: Perform at least one iteration of source scan procedure on all towers Use LED and Laser runs to complete pre beam calibration Use isolated tower slope analysis to “fine tune” calibration during STAR collisions.

Commissioning Goals: 

Commissioning Goals Timed in 3 crates of FEE electronics Receiving STAR triggers into miniDaq Included in STAR data stream Slow Control Software allows for masking of hot towers for trigger. DSMs programmed and tested. Software has been developed to monitor the DSM inputs. High Tower Trigger commissioned and included in transverse pp production trigger FEE proms allow pedestal subtraction for Jet Patch Triggering and slow control software provides look up tables for positioning of trigger patch sum pedestals. Coming Soon! – Jet Patch Trigger commissioning

EEMC High Tower Trigger: 

HT 1 HT 2 ENDCAP response during STAR Run #4126026 with ppTrans1 trigger EEMC High Tower Trigger High Tower 1 Threshold ADC=192 ~2.6 GeV assuming Sampling Fraction = 5% HT1 rate  44 Hz for BBC coin rate = 54 kHz High Tower 2 Threshold ADC=320 ~ 4.6 GeV assuming SF = 5% HT2 rate  3.5 Hz for BBC coin rate = 54 kHz

Jet Trigger Preparation: 

Jet Trigger Preparation The original proms in the FEE FPGA dropped the lowest 4 out of 12 ADC bits from each tower before summing groups of 6, 8 or 10 to make Trigger Patch (TP) Sums. Since the average tower pedestal is located in channel 10-30, the TP sum pedestal was smeared out by towers whose pedestals crossed the 4 bit line. The yellow plot shows the width of a Jet Patch Sum (15 TP sums) Pedestal. This width varies with pedestal movement and prohibits applying a uniform jet trigger threshold. New proms, which have been burned and loaded to each FEE board, effectively allow for each tower pedestal to be set to channel 24. This results in a 1 channel wide jet patch pedestal as shown in the blue plot. This will allow for thresholds as low as 3 GeV to be set uniformly across the detector. Layer 1 DSM word Layer 1 DSM word