Triple GEM Beam Test within PHENIX

DC Upgrades Meeting 4/14/04

B. AzmounPHENIX

Brookhaven National Lab

4/14/04 B. Azmoun 2

Outline

• Basic format of presentation: Timeline of tests performed with triple GEM detector in and out of close proximity to A-A beam in PHENIX.– Simple Survival test (trips, sparks)– Performance Evaluation (Gain, Stability, Response to beam-beam collisions)

• Data acquired with GEM detector mounted in various orientations within central region of PHENIX.– Self Triggered Fe-55 Spectra– Beam-Beam Triggered Data (Correlation between Beam collisions and GEM hits)

• Comparison of: Fe-55 Peak Position, abs. Signal Gain, %Res.(FWHM), and Background:– Lab Vs. PHENIX Data – Beam ON Vs. Beam OFF Data– Magnet (Inner/Cent.) ON Vs. Magnet OFF Data

• Objective:Objective: To monitor the behavior of a triple GEM detector within the PHENIX interaction region, and to compare these results with in-lab tests.

4/14/04 B. Azmoun 3

Layout of Triple GEM DetectorGases Used

• Ar/CO2 (70/30)

> Volt Configuration:DG: 0.5kV/cm

TG1:2.5kV/cm

TG2: 3.0kV/cm

IG: 3.5kV/cm

> Nominal Operating Gain:~6.5x103 @ Foil Pot. = 360V

• CF4

> Volt. Configuration:DG: 0.5kV/cm

TG1:2.5kV/cm

TG2: 3.5kV/cm

IG: 5.0kV/cm

> Nominal Operating Gain:~3.2x103 @ Foil Pot. = 495V

Std. Conical, Segmented

CERN Foils

Active area of pads ~1.0x1.5cm

Photos of detector in place within PHENIX

Det. Mounted near N. Cent. Mag.

Det. on MVD lifting table,Mylar window Facing Upright

4/14/04 B. Azmoun 5

Lab Test Data• Data taken in the lab provides a baseline measurement.

Timeline Start:

Run#: 1 (Lab)Date: 3/2/04Gas: Ar/CO2 (70/30)HV ON: 1:30 pmData Run: 2:50 pmFoil Pot. = 360VGain= 5923 , Res.= 25%BEAM: N/A, ZDC = N/ABeam Cond: N/AMag: N/A

• Gas: Ar/CO2 (70/30)

HV: ON

Data Run Parameters

Fe-55 Spectrum

4/14/04 B. Azmoun 6

GEM Det. Mounted in inner central region of PHENIX

Orientation #1:•Gas: Ar/CO2 (70/30)

Beam: OFF, Mags: OFF HV: ON

Com parison of Gain Curves

10

100

1000

10000

100000

310 320 330 340 350 360 370 380Foil Potential [Volts]

Abs

olut

e G

ain

Lab

Beam Test @PHENIX

Run#: 2Date: 3/3/04Gas: Ar/CO2 (70/30)HV ON: 1:00 pmData Run: 5:20 pmFoil Pot. = 360VGain= 6070 , Res.= 37%BEAM: OFF, ZDC = 0HzBeam Cond: Mag: OFF

Isolation Trans. Mounted onto Det.

Spect. ~ identical to lab data, but inc. peak width

PedestalCalib. Pulse

4/14/04 B. Azmoun 7

Run#: 5Date: 3/4/04Gas: Ar/CO2 (70/30)HV ON: 1:05 pmData Run: 6:25 pmFoil Pot. = 360VGain= 6827 , Res.= 34%BEAM: OFF, ZDC = 0HzBeam Cond: Mag: OFF030404_360_241.txt

Run#: 3Date: 3/4/04Gas: Ar/CO2 (70/30)HV ON: 1:05 pmData Run: 3:35 pmFoil Pot. = 320VGain= 187 , Res.= 56%BEAM: OFF, Au I = 35x109

Beam Cond: Mag: ON030404_320_8p7.txt

Run#: 8Date: 3/17/04Gas: Ar/CO2 (70/30)HV ON: 8:10 amData Run: 9:00 amFoil Pot. = 360VGain= 6176 , Res.= 40%BEAM: OFF, ZDC = 0HzBeam Cond: Mag: OFF

•Variation in position of main peak is within normal limits (<+/-10%)

Beam Dumped

Beam: ON, Mags: ON

~ Consistent Response 13 days later

HV: ON Beam: OFF, Mags: OFF

END of END of Fill #1Fill #1

320 V

(This was the only spectrum measured during fill #1, before the beam dump.)

Survival Test: Passed (GEM exhibits normal behavior near beam)

4/14/04 B. Azmoun 8

Orientation #2:•Gas: Ar/CO2 (70/30)

Run#: 9Date: 3/17/04Gas: Ar/CO2 (70/30)HV ON: 11:25 amData Run: 11:55 amFoil Pot. = 360VGain= 6823 , Res.= 35%BEAM: OFF, ZDC = 0HzBeam Cond: Mag: OFF

HV: ON Beam: OFF, Mags: OFF

Isolation Transformer moved outside of PHENIX field boundaries, to DAQ in

PHENIX rack room for orient. 2, 3, and 4.

Similar Spect. Compared to Orient. #1

4/14/04 B. Azmoun 9

Run#: 10Date: 3/17/04Gas: Ar/CO2 (70/30)HV ON: 11:25 amData Run: 1:45 pmFoil Pot. = 360VGain= 6845 , Res.= 33%BEAM: OFF, ZDC = 0HzBeam Cond: Mag: ON

Run#: 14 (BB trig. Data)Date: 3/18/04Gas: Ar/CO2 (70/30)HV ON: 4:40 amData Run: 7:00 amFoil Pot. = 360VFract. of events above ped. = 4.4%BEAM: ON, ZDC ~2.6kHzBeam Cond: Mag: OFF

•Variation in position of main peak is within normal limits (<+/-10%)Magnets ON do not affect data !

Mags: ON

Run#: 12Date: 3/18/04Gas: Ar/CO2 (70/30)HV ON: 4:40 amData Run: 5:40 amFoil Pot. = 360VGain= 6172 , Res.= 38%BEAM: ON, ZDC = 3.56kHzBeam Cond: Mag: ON

Inc. in backgnd.

Beam: ON, Mags: OFF>>ON HV OFF>>ON

Fill #2Fill #2END of END of Fill #2Fill #2

Fract. of events above ped. (~ch.70) = 4.4%

Beam-Beam Triggered Data

Ped.

4/14/04 B. Azmoun 10

•Gas: Ar/CO2 (70/30), CF4

Orientation #3:

Run#: 15 (BB trig. Data)Date: 3/19/04Gas: Ar/CO2 (70/30)HV ON: 1:00 amData Run: 1:47 amFoil Pot. = 360VFract. of events above ped. = 4.6%BEAM: ON, ZDC = 1.56kHzBeam Cond: Mag: ON

Run#: 16Date: 3/19/04Gas: Ar/CO2 (70/30)HV ON: 1:00 amData Run: 2:13 amFoil Pot. = 360VGain= 5540 , Res.= 43%BEAM: ON, ZDC = 1.47kHzBeam Cond: Mag: ON

Large Inc. in background (as well as Dec. Gain)

4.6%Fill #3Fill #3

Ar/CO2 (70/30)

Beam: ON, Mags: ON

4/14/04 B. Azmoun 11

Switch to CF4

HV OFF>>ONRun#: 17Date: 3/19/04Gas: CF4

HV ON: 5:50 amData Run: 6:41 amFoil Pot. = 495VGain= 3200 , Res.= 79%BEAM: ON, ZDC = 2.48kHzBeam Cond: Mag: ON

Run#: 18 (BB trig. Data)Date: 3/19/04Gas: CF4

HV ON: 5:50 amData Run: 6:51 amFoil Pot. = 495VFract. Of events above ped. = 2.7%BEAM: ON, ZDC = 2.40kHzBeam Cond: Mag: ON

Run#: 19Date: 3/19/04Gas: CF4

HV ON: 5:50 amData Run: 7:08 amFoil Pot. = 495VGain= 3277 , Res.= 83%BEAM: OFF, ZDC = 0HzBeam Cond: Mag: ON

Bkgnd. Persists during CF4 Runs, but is relatively smaller

Smaller Number of Counts compared with Ar/CO2

Dec. in Bckgnd.

Beam: OFF,

Mags: ON

(HV Remains ON)

2.7%

Mags /HV Trip

END of END of Fill #3Fill #3

4/14/04 B. Azmoun 12

Run#: 21 (BB trig. Data)Date: 3/19/04Gas: CF4

HV ON: 7:28 amData Run: 9:05 amFoil Pot. = 495 VFract. of events above ped. = 5.1%BEAM: ON, ZDC = 4.42kHzBeam Cond: Mag: ON

Run#: 22Date: 3/19/04Gas: CF4

HV ON: 7:28 amData Run: 10:24 amFoil Pot. = 495VGain= ? , Res.= ?BEAM: ON, ZDC = 2.77kHzBeam Cond: Mag: ON

(Overflow count rate inc.)Run#: 20Date: 3/19/04Gas: CF4

HV ON: 7:28 amData Run: 7:57 amFoil Pot. = 495VGain= 2758 , Res.= 104%BEAM: OFF, ZDC = 0HzBeam Cond: Mag: ON

Large Inc. in Backgnd.

HV: OFF>>ON

Mags. OFF>>ON (Beam Remains OFF)

Inc. in number of counts above ped.

Beam ON

Peak lost in Backgnd ... Beam related ??

5.1%Fill #4Fill #4

4/14/04 B. Azmoun 13

Run#: 24Date: 3/19/04Gas: CF4

HV ON: 11:40 amData Run: 11:50 amFoil Pot. = 495VGain= 3206 , Res.= 73%BEAM: OFF, ZDC = 0HzBeam Cond: Mag: OFF

•Other than some anomalies (e.g. run 16), possibly related to inc.’d background, the variation in the position of the main peak is within normal limits (< +/-10%).

Run#: 23Date: 3/19/04Gas: CF4

HV ON: 11:40 amData Run: 11:46 amFoil Pot. = 495VGain= 3129 , Res.= 77%BEAM: ON, ZDC = 1.97kHzBeam Cond: Mag: OFF

Peak Recovered after HV OFF/ON, (Mag OFF, Beam still ON)

HV: OFF>>ON Mags: OFF

Dec in Backgnd.

Beam Dumped

END of END of Fill #4Fill #4

4/14/04 B. Azmoun 14

•Gas: CF4

Orientation #4:

Run#: 25Date: 3/19/04Gas: CF4

HV ON: 1:09 pmData Run: 1:12 pmFoil Pot. = 495VGain= 3219 , Res.= 76%BEAM: OFF, ZDC = 0HzBeam Cond: Mag: ON

Similar to Orient. 3, with beam OFF, Mags ON

Beam: OFF, Mags: ON

4/14/04 B. Azmoun 15

Run#: 26Date: 3/19/04Gas: CF4

HV ON: 1:09 pmData Run: 3:24 pmFoil Pot. = 495VGain= 3155 , Res.= 72%BEAM: ON, ZDC = 5.7kHzBeam Cond: Mag: ON

Run#: 27(BB trig. Data)Date: 3/19/04Gas: CF4

HV ON: 1:09 pmData Run: 3:47 pmFoil Pot. = 495VFract. of events above ped. = 0.22%BEAM: ON, ZDC = 5.35kHzBeam Cond: Mag: ON

• Variation in the position of the main peak is within normal limits (< +/-10%).

Lower backgrnd. Compared to Orient. #3

Beam: ON

Dec. in number of counts above ped.

0.22%Fill #5Fill #5END of END of Fill #5Fill #5

4/14/04 B. Azmoun 16

Gain Stability• The following plot depicts the

variation in gain at a constant field potential within Ar/CO2 and CF4 during the series of measurements presented in the previous slides.

Gain Stability of Sm all-CERN triple GEM in different gases, using a ~10Hz Fe-55 Source

0.8

0.9

1

1.1

1.2

1.3

1.4

0:00 0:28 0:57 1:26 1:55 2:24 2:52 3:21

Elapsed Tim e after HV is applied [hr:m in]

Rel

ativ

e ga

in

Ar/CO2 (80/20)

CF4

• Gain variations are mainly due to two factors:

1. Fluctuations in physical parameters like temperature, pressure, etc.

2. Before arriving at a steady state value, the gain initially continues to grow due to a charging effect within the Kapton foil, after the HV is applied (see the example to the right).

Gain Stability @ Const. Gain

0

0.2

0.4

0.6

0.8

1

1.2

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28

Run #

Gai

n N

orm

aliz

ed to

Lar

gest

Val

ue

Ar/CO2 (360V)

CF4 (495V)

Low transient Gain due to charging effect

Large Gain Drop ???

4/14/04 B. Azmoun 17

% Res. Vs. Data Run% Res. (FWHM) Vs. Data Run

0

20

40

60

80

100

120

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28

Run #

% R

es. [

%]

Ar/CO2 (70/30)

CF4

LAB

320 V

RUN #22: Peak Lost in Bckgnd.

4/14/04 B. Azmoun 18

Scaler Rates near PHENIX: 3/19/04

Anomalous Behavior of Det. (Run 21- 22)

4/14/04 B. Azmoun 19

Summary• The GEM detector performed smoothly within the central

region of PHENIX using both Ar/CO2 (70/30) and CF4– trouble free operation at reasonable gains in both gases – no sparking or excessive gain instabilities with beam ON, or during a

beam dump

• No observed effect in detector operation due to magnetic field

• Detector sees low energy, beam related background when positioned close to the beam (primary signal < 100 e’s) – possibly less sensitive with CF4

• The detector appeared to be sensitive to beam conditions– large increase in low energy background seen during one fill with CF4,

but decreased dramatically at other times (so far cannot correlate this with scalers of background counters--see slide #18)