1Apr. 28, 2007

Test of the Pulse Height and Time Jitterfor the IHEP Full-Size RPC’s

with 8-m-Long Readout Strip Planes

C. Lu, K. McDonald and W. Sands

Princeton University

2Apr. 28, 2007

4-Layer RPC Stack

3Apr. 28, 2007

Planar Arrays of Chambers

Mount chambers in 4 planes, staggered to maintain high efficiency.

Readout in 4 quadrants with 9-m-long readout strips.

All electronics at the edge of the array.

Simplified mechanics of chamber mounting.

4Apr. 28, 2007

Effect on Efficiency

Dead regions between adjacent chambers in one plane 3% reduction in efficiency of that plane (95% 92%).

With staggering of different planes, correlated inefficiency between a pair of planes will be ~ 0.1%.

3 out of 4 trigger efficiency is 96.5% (down from 98.6%).

5Apr. 28, 2007

Readout via Long Transmission Lines

Long readout strips act as transmission lines signal quality independent of position if strips properly terminated.

Lab tests confirm this (rest of this presentation).

If strip width remains at nominal 25 cm, can reduce number of readout channels by factor of 4.

(Or, can increase position resolution by factor of 4 if keep channel count the same.)

6Apr. 28, 2007

Test setup

IHEP single gap RPC chamber

Readout strip

Rigid honeycomb panel (1/2” thick)

Al sheet underneath of the honeycomb as ground shielding and strip signal return plane.

Al foil to shield the 8m long strip plane.

7Apr. 28, 2007

Flexible readout strip band

This is Belle readout strip band, can make large roll of this material.

8Apr. 28, 2007

Honeycomb panel

½” thick honey comb panel, very rigid, surprisingly its dielectric constant is ~3.80.

9Apr. 28, 2007

Signal shape

R1=165Ω,R2=38Ω

RPC1 HV ON

R1=165Ω,R2=2Ω

RPC1 HV ON

R1=165Ω,R2=12Ω

RPC1 HV ON

Terminator’s effect on the signal’s shape

10Apr. 28, 2007

Test TDC and ADC simultaneously

Use CAMAC TDC and charge sensitive ADC modules to test the 8m long strip readout signal.

11Apr. 28, 2007

Meantimer Time spectrum

The trigger counters are 1m long, therefore the TDC start signal has intrinsic time jitter. We use LeCroy Meantimer modules to eliminate this jitter. Two trigger counters are overlapped, their outputs enter the LeCroy meantimer, its output signal corresponds to the signal initiated at the middle of the counter.

10ns/division

Input #1 of the meantimer

Input #2 of the meantimer

Triggered by output of the meantimer

12Apr. 28, 2007

Trigger counters at far end of the strip plane

First we place the trigger counters at the far end of the readout strip plane. Near and far end trigger arrangements are shown below:

13Apr. 28, 2007

Screen capture of the strip signal

80ns/div

50mV/div

The screen captures on the left show several sequentially captured trigger events w/o any other selection.

14Apr. 28, 2007

TDC and QDC spectrum

We used a LeCroy TDC module and a Phillips QDC module to measure the time and charge spectrum of the full size RPC chamber.

Put the trigger counters at the far end of the strip plane.

The time jitter for a 1m long section of RPC is ~6.5ns

15Apr. 28, 2007

Trigger counters at near end of the strip plane

Screen captures of strip signal for trigger counters at the near end.

16Apr. 28, 2007

TDC and QDC spectrum

(1 ch = 0.125pC)

17Apr. 28, 2007

Peak sensing ADC module test results

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TDC(ch)

TDC, 7400VMean=1041 chSigma=155 ch

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TDC, 7600VMean=971chSigma=110ch

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TDC, 7800Vt=928chs=96.5ch

Change HV setting, keep other electronics system fixed, we can see that ADC peak is shifting towards right, and TDC peak is shifting towards left while raising HV from 7400V to 7800V.

ADC calibration:

PH(mV)=(ADC(mV)+31)/0.7

18Apr. 28, 2007

Correlation between ADC and TDC

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ADC

TDC

7800V

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ADC

TDC

7400V

Plot the scatter plot of ADC vs TDC, we found that TDC is quite constant. It does not depend on the ADC reading:

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ADC

TDC

7600V

19Apr. 28, 2007

OPERA RPC system uses 8m long readout strip plane, the following pages show few steps of their installation procedure and the dimension of their strip plane.