1

A.Andronic1, H.Appelshäuser1, V.Babkin2, P.Braun-Munzinger1, S.Chernenko2, D.Emschernmann3, C.Garabatos1, V.Golovatyuk2, J.Hehner1, M.Hoppe4, E.Jimenez1, M.Kalisky1, C.Lippmann1, D.Moisa5, F.Uhlig1, M.Petris5, M.Petrovici5, A.Radu1,5, V.Simion5, R.Simon1, H.-K.Soltveit3, J.Stachel3, H.Stelzer1, A.Wilk4, J.P.Wessels4, Yu.Zanevsky2, V.Zhezher2 and V.Zryuev2

High rate beam test of Gas Detectors

1GSI Darmstadt; 2JINR Dubna; 3University of Heidelberg, 4University of Münster, 5NIPNE Bucharest

Results of experimental data analysis taken on the SIS GSI beam are presented. As a prototype of TRD detector, four proportional chambers of different configurations and one GEM detector were used. The main goal of experiment was studying the behaviour of detectors response under irradiation by high intensity beams.

2

Fig.1 Layout of the detector installation on the beam line

Description of the experimental setup

Detector typeActive area

(mm)Pitch

(μm)Number of planes

Detector “s task (destination)

Scintillation counters 50 x 40 - 2Trigger, beam

intensity monitor

Microstrip detectors 32 x 32 50 2x, 2yBeam shape

control

Parameters of beam monitoring detectors

3

Fig.2. Layout of MWPC prototypes. Left panel: chambers built at GSI and Bucharest, right panel: chamber built in Dubna.

3mm

2mm

1mm

1mm

3 4 1 2

6 5 7 8

Fig. 3. The scheme of the GEM detector used as a prototype for CBM TRD

Holes are bi-conical with external diameter 70 μm, internal – 50 μm , pitch – 140 μm

wire pitch(mm)

anode-cathode

gap(mm)

drift region(mm)

pad size(mm)

active area( cm2 )

GSI-1 2 3 0 7.5 x 80 48

GSI-2 4 3 0 7.5 x 80 48

Bucharest 2.5 3 0 7.5 x 80 48

Dubna 2 2 8 3.0 x 4.0 1.92

Mechanical parameters of MWPC’s used in the TRD test beam.

40 mm

50

mm

10

25

Active area of GEM

4

5

Fig.5. Beam intensity distribution during the spill.The figures represent the case when extraction

time was 0.15 and 2.0 sec.

0.15 sec

The information from the upstream scintillation counter which covers the beam also was used for a total beam intensity estimation. Number of counts in this counter happened in time from the previous trigger was recorded.

Having in addition information from the clock about time between triggers we are able to recover the time structure of the beam passed through our detectors.

2.0 sec

Beam Intensity estimation

6

Average pulse shape from FADC (50 bins x 30 nsec) for different readout chambers and different spill length

7

Steps of Data Analysis

1. “Track” reconstruction with help of two Si (x and y strips with 50 μm pitch) stations.

2. Calculation expected track coordinate in each detector

3. Search for signals beyond the threshold around expected position

4. Calculation residuals R = Xexp – Xcoor

5. Calculation the total charge (sum up the signals from adjacent strips (pads))

6. Calculation of center of gravity using signals from adjacent strips, (σ ~ 0.4 - 0.6 mm)

7. Check the track validity using addition coordinate information from proportional chambers

Selection of tracks which have small residuals on selecteted chambers.

xx x

xx x xx

xx

xxx

Si-1(x,y) Si-2(x,y)

GSI-1 GSI-2 PC-Bucharest PC-Dubna GEM

8

30 mm

7 mm

Strip position of GSI-1 chamber defined with Si “tracker”

Pads position of Dubna’s MWPC defined with Si “tracker”

3 mm

4 mm

Pads position of GEM defined with Si “tracker”

10mm

9

GEM

Ar/CO2

GEM

Xe/CO2

Dubna

Xe/CO2

Dubna

Ar/CO2

10

Xe/CO2

GSI-1 GSI-1

GSI-2

Xe/CO2

Ar/CO2

GSI-2

Ar/CO2

11

Stability of the charge of signal from GEM and Dubna chamber vs beams intensity.

12

Stability of the charge of signal from GSI chambers vs beam intensity

13

Dubna, X-direction

Ar/CO2

Dubna, Y-direction

Xe/CO2

Pad numbers distribution in Dubna Chamber (Ar/CO2)

Dubna, Y-direction

Ar/CO2

Dubna, Y-direction

Ar/CO2

Dubna, X-direction

Ar/CO2

14

Space resolution vs beam Intencity

(Dubna chamber)

15

Conclusions

1. We did not observe a gas gain degradation up to intensity of 100 kHz/cm² in MWPCs with Ar/CO-2 and Xe/CO-2 mixtures.

2. We did not observe a spatial resolution worsening vs beam intensity for Dubna chamber (with a small pad size). A contribution of multiple scattering is significant in obtained spatial resolution for MWPCs (especially for Dubna chamber). 3. Pad size of MWPC should be optimized for the next beam test

16

• Minimize a multiple scattering • Use fast 2D coordinate detectors for beam profile definition (GEM)• Provide beam intensity variation with a long spill length (2 sec)• Try to decrease size of the beam (1-2 cm² ).• Increase number of DAQ channels.

For the next Run we need to

2 sec

Beam intensity

Beam extraction lenght

Detectors(Dubnа)

Sense wire step мм

Cathode wires stepмм

Anode-Cathode gap мм

Readout pad size мм2

MWPC(2 chambers)

2 0.5 3 5 x 20

GEM 10 x 10