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MM Gain measurements with MBT3/4 chambers

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MM Gain measurements with MBT3/4 chambers

• By using an MiniX-Ray Gun (Ag), we want to measure the gain in the MBT3 and MBT4 chambers used in ATLAS during 2012 run.

• The X-Ray generated by the MiniX-Ray system are more penetrating than the X-Ray produced by the Cu X-Ray gun, this allow us to measure the gain of the MBT3/4 at the same time under different X-Ray flux conditions but with the same environmental conditions.

• We need to estimate the rate of the “primary electrons” generate by the flux of the incoming X-Ray.

• The MMs gain is measured as a function of the HV.

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MBT chambers layoutGas Distribution

HV 9 mm

4.5 mm 4.5 mm

Common Drift Electrode

2 APV card used for each MBT chamber (256 channels).Channels map organized in order to reconstruct X coordinate from 1-200 ch. and V ch. from 201 to 256.

2D Readout system, X and V coordinate

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X-Ray / MM chamber setup

MM

HV Side

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MBT3/4 Scanning conditions

• The chambers were scanned using the MiniX-Ray gun.

• To apply HV on the resistive strips and the drift, the CAEN SY2527 and A1821 boards were used.

X-Ray gun:HV = 30.00kVBeam intensity = 12 microA

HV-resistive strips = +450 to +550VHV-drift = -300V(monitored by power supply)

• Two HV scans have been performed with MBT3 or MBT4 in front of the X-Ray gun.

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Collected DataHV [Volt]

MBT4 (1° chamber) MBT3 (1° chamber)

450 200605 200681460 200606 200682470 200607 200683480 200608 200684

490 200609 200685

495 200610 xxxxx

500 200611 200686

505 200612 xxxxx

510 200613 200687515 200614 200688520 200615 200689525 200616 200696530 200617 200697535 200618 200692540 200619 200693545 200620 200694550 200621 200695

100 K events for each run

Total readout window for run 0.0675 s

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Amplification Current Vs HV

440 450 460 470 480 490 500 510 520 530 540 550 5600

500

1000

1500

2000

2500

f(x) = 0.000742661106903644 exp( 0.0272075724291114 x )

f(x) = 0.000139426197612421 exp( 0.0292224888624651 x )

Amp. Current Vs HV

MBT3Exponential (MBT3)MBT4

HV [Volts]

Cu

rre

nt [

nA

]

440 450 460 470 480 490 500 510 520 530 540 550 560 5700

500

1000

1500

2000

2500

3000

3500

Amplif. Current Vs HV

MBT3 Current

MBT4 current

HV [Volts]

Cu

rre

nt [

nA

]

MBT4 in front to the X-Ray Gun

MBT3 in front to the X-Ray Gun

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Gain MeasurementsG = Cf/ Ci

For a single event we define the GAIN as follow:Cf = Final ChargeCi = Initial Charge

We can extract the total Final Charge from the current delivered by the power supply.

The number of reconstructed clusters (per second) gives us the rate of the converted X-Ray

From each converted X-Ray we expect ~ 500 electrons (13 KeV / 26 eV)

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Initial Cluster selection“ True” Clusters

“ True” Clusters

“ Noise” Clusters

Applied cut “cl qmax>100” andCluster size > 1, to remove noise clusters

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Initial Cluster selection

440 450 460 470 480 490 500 510 520 530 540 550 560 5700

20000

40000

60000

80000

100000

120000MBT3 Cluster Vs HV

MBT3 cl_width>1MBT3 nclu cl_qmax > 100

HV [Volts]

Clu

ste

r [C

ou

nts

]

440 450 460 470 480 490 500 510 520 530 540 550 560 5700

50000

100000

150000

200000

250000

MBT4 Cluster Vs HV

MBT4 nclu cl_qmax > 100

MBT4 cl_width>1

HV [Volts]

Clu

ste

r [C

ou

nts

]

MBT4 close to the X-Ray gun

MBT3 far from the X-Ray gun

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Initial Cluster selection

MBT4 far from the X-Ray gun

MBT3 close to the X-Ray gun

440 450 460 470 480 490 500 510 520 530 540 550 560 5700

50000

100000

150000

200000

250000

MBT3 Cluster Vs HV

MBT3 cl_width>1MBT3 nclu cl_qmax > 100

HV [Volts]

Clu

ste

r [C

ou

nts

]

440 450 460 470 480 490 500 510 520 530 540 550 560 5700

20000

40000

60000

80000

100000

120000MBT4 Cluster Vs HV

MBT4 nclu cl_qmax > 100

MBT4 cl_width>1

HV [Volts]

Clu

ste

r [C

ou

nts

]

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Chamber Gain Vs HV

440 450 460 470 480 490 500 510 520 530 540 550 560 5700

2000

4000

6000

8000

10000

12000

14000

MBT3/MBT4 Gain Vs HV

Gain MBT3

Gain MBT4

HV [Volts]

Ga

in

440 460 480 500 520 540 5600

2000

4000

6000

8000

10000

12000

14000

MBT3/4 Gain

Gain MBT3

Gain MBT4

HV[Volts]

Ga

in

MBT3 close to the X-Ray gun

MBT4 close to the X-Ray gun

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Summary A first MM gain measurement, using Ag Mini X-Ray system as been done with

MBT3/4 chamber. First source of uncertainty for this measure come from the incoming charge

estimation:•Number of conversion for second.•Number of “primary” electrons for each conversion.

A small difference of gain, equivalent to 10 Volts, seems to be present between MBT3/MBT4 ( the effect is more evident in the second scan).

The gain has not been corrected for the possible HV drop as a consequence of the high current generate by the high flux and for environmental variations between the two different scans.

Same measurements can be performed with Cu X-Ray gun, in this case we can study only one chamber for each scan.

Next steps: •Evaluation of the voltage drop effect on.•Gain measurements and characterization as a function of the environmental conditions.•Gain measurements for T and L chambers.