Analysis of Pion beam test

Analysis of Pion beam testR.Sawada

20/Jan/2004on VRVS

Q.E. estimationEnergy ResolutionTiming Resolution

2

Absorption

Xenon was very pure !

distance dependence ofnumber of photoelectrons at each PMT normalized with MC.

3

Q.E. estimation

gasalpha in gas

TERAS in 2003gain ~ 5e6

liquidalpha in liquid

PSI in 2003gain ~ 1e6

beam on (FSH52 =125)

We have ever used gas data for Q.E. estimation.But now we can also use liquid data because Xe is pure.

Q.E. (liquid ~ -105℃) ~ 0.74 * Q.E. (gas ~ -85℃)

4

Comparison between data and MC

alpha Pi0->2gamma

Q.E. estimated from liquid alpha data was used in MC.

The peak position is well reproduced by this MC code.

data

MC

data

MC

Energy Resolution

6

Data Condition

with paraffin shield

Collimator sizeXenon 9.5 cmNaI 11.5 cm

FSH52 DAC value(beam intensity)

125

PMT gain 1e6

7

cut & correction

Nfpmt(0.5) is used as depth parameter for correction and cut.

Nfpmt : number of PMTs which occupy the half of Qfront.

sigma2<90 is also applied to remove very deep events.

MC

Nfpmt(0.5)>4

rejected

accepted

8

Energy Resolution

FWHM = 4.5 ± 0.3 (left:2.7 + right:1.8) %

•Depth cut and correction.

•55 MeV gamma is selected by NaI energy cut.

•Impinging position cut is also applied

•(sqrt(x_average^2 + y_average^2)< 1.5cm)

(sigma of the right part is 1.53%)

9

Position dependence of resolution

FWHM [%]

4.3±1.0

4.8±0.4

4.6±0.7

4.5±0.6

4.5±0.3

4.5±0.6

4.1±0.9

5.0±0.5

5.0±1.6

center ofthe detector

center ofF14

center ofF21

center ofF20

center ofF15

There is no positioin dependence of resolution.

10FWHM is constant if depth > ~4cm

Resolution is estimated with slicing with depth parameter. Correspondence of depth parameter and the depth is calculated from MC.

11

Masking effect

1 without masking

2 mask: edge of front

3 mask: edge of front top,bottom

4 mask: edge of front top,bottom right,left

gamma

Some PMTs are masked to simulate the curved shape of the final detector. Curved shape is corresponding between 1 and 3 (it depends on how to put PMTs).

Timing Resolution

13

Data Condition

without Amplifier

Collimator sizeXenon 9.5 cmNaI 11.5 cm

FSH52 DAC value(beam intensity)

125

PMT gain ~5e6

14

Timing Counter (TC)

Timing resolution of the timing counter

is 60 psec

•Time walk correction.•virtex correction with Nphe(light)/Nphe(right)

•2 × 5cm × 5cm × 1cm BC404• 4 × 1-inch finemesh type PMTs• 5cm × 5cm × 0.6 cm lead target

15

Algorithm

Timing correction of each PMT•time walk

•vertex (x_average,y_average,sigma2)

Timing of each PMT is shifted so that mean become 0.

Taking the average with•software threshold : 20 nphe•weight : sqrt(ADC)

TDC’(i) = TDC(i) - TDC(TC)

16

Timing resolution (right - left)

Resolution is 75 ± 4 psec (5e6 gain)

•Depth cut is the same as energy analysis.

•No impinging point cut is applied.•Energy cut for selecting 55MeV gamma is applied.

Compared the timing of each part after

dividing the detector to right and left.

(fluctuation from the first conversion depthdistribution is not included in this resolution)

17

Timing resolution (Xe - TC)

Resolution issqrt(128^2-60^2) = 113 psec

(5e6 gain)

Time resolution is also estimated from the difference between the Xenon and the timing counter.

The difference from the analysis(right-left) can be the resolution of depth reconstruction (~70psec).

Timing has no correlation with depth because it is corrected for each PMTs before taking the average. If we don’t correct depth correlation, it is like the right figure.

18

Timing resolution with 1e6 gain + Amplifier

gainbeam

intensity(FSH52 DAC)

time resolution

(right - left) [psec]

time resolution (Xenon - tc)

[psec]

w/o Amp 1e6 350 391 ± 11 426.8 ± 11

w/ Yuri’s Amp 1e6 125 251 ± 6 295 ± 6

w/ Lecce Amp 1e6 125 246 ± 6 300 ± 7

w/o Amp 5e6 125 197 ± 6 256 ± 7

Time resolution using 8 PMTs which is applied amplifiers.

Amplifier improve the resolution at 1e6 gain.

19

Summary

Q.E. is estimated from liquid data to take into account the decrement of it under backgrounds.

Energy resolution is estimated as 4.5 ± 0.3 %. There is no strong dependence on impinging position or depth. (if depth > ~4cm)

Energy resolution is estimated with masking some PMTs to simulate curved shape. The effect must not be so large.

Timing resolution of (right -left) is 75 psec

Timing resolution of (Xe - TC) is 113 psec. We need more sophisticated way to reconstruct the depth.

Amplifier will improve timing resolution at 1e6 PMT gain.