development of timing rpcs presented by p.fonte for the tof-rpc group

Development of timing RPCs

Presented by P.Fonte

for the TOF-RPC group

CBM meeting 8.3.2005 - TOF-RPCCBM meeting 8.3.2005 - TOF-RPC

OutlineCurrent activities of the TOF-RPC group Test facility at ELBE/Rosendorf

Physics simulation studies

RPC propertiesAnalytic model of the RPC rate properties (NEW - post TSR)Aging tests

Improvement of the rate capability by using semiconducting glassesby using commercially available ceramic materials (NEW)through temperature increase

RPC layout optionsSingle cell chambersShielded timing RPCsMultistrip counters

Readout electronicsPreamplifier/discriminatorFOPI-RPC electronicsTime measurement and digital backend


Test facility at ELBE/Rosendorf

The Rossendorf electron accelerator ELBE provides electrons up to 40 MeV in beam packets with a time spread better than 10 ps.

Ready for users!


Physics simulation,K,p momentum distributions

Occupancy on TOF plane


RPC propertiesAnalytic model of the RPC rate properties (NEW)

Aging


)'2('1

')( )(

01)(0

)exp()(

'0

0

th

th

thth

enIen

e

e

nn

)(/)'( 0 Esnt ))1(log('0 effn

driftvS

Primary statistics

Gas response

[A. Mangiarotti, P.Fonte, A.Gobbi NIM A 533(2004)16]

σ τ(n 0’

) [1

/s u

nits

]

n0’

Ineff (%)Analytical model of the rate effect (NEW)


gapE

Et dE

dS

SdE

d

SS

var

1var

1var

2

2

2

Intrinsic time resolution Fluctuations in the field Drop in the field

[Mangiarotti et al. NIM A 535 (2004) 272 ]

(varE)1/2 /E

σ τ(n 0’

) [1

/s u

nits

]

Analytical model of the rate effect (NEW)

For any sourceof E variation


HV = 3.1 kV/gapHV = 3.2 kV/gapHV = 3.3 kV/gapHV = 3.4 kV/gap

NOT FITTED!

FITTED

Data [re-scaled ‘prompt charge’]

Analytical model of the rate effect (NEW)


Aging (2002-2003) - humid, cold

After accumulating 800mC/cm2 (equiv. 8.5 years of normal operation) we don't observe any systematic long-term increase of dark current with time.

made some changes on the experimental setup.

• 6 counters

• Room temperature

• “Standard” timing

RPCs gas

85%C2H2F4+10%SF6+

5% iso-C4H10, with

10% relative humidity

• Primary charges were

created by an UV lamp

No problem up to ~8 years equiv. charge (800 mC/cm2)


Aging (2004-05) – humid, hot

• After more than 80 days we don’t observe any increase of the dark current.

• Which seems to stabilize.

• In chambers that operate at more than 2 kHz cm-2.

•And accumulated 200 mC cm-2

No problem so far (90 days = 200 mC/cm2)

Tenfold higher current


Improvement of the rate capability (0.4 to 20 kHz/cm2 foreseen, current designs: 1 kHz/cm2)

by using semiconducting glassesby using commercially available ceramic materials (NEW!)

through temperature increase


Rate / semiconducting glass

Silicate glass Phosphate glass


Rate / semiconducting glass


Rate / ceramics (NEW)

Commercial “controlled resistivity” alumina, Al940CD, from Wesgo® Ceramics

Volume resistivity between 1×109 and 2×109 cm at room temperature. Seems to be electronic conductor (no charge-up effects). Good (hard, dense) surface. Not straightforward (~1 year R&D)

Benchtop test setup

22Na

Reference Chamber(identical)

Test Chamber10 cm2

(CBM granularity)

X-ray Generator

Photon conversion on RPC yields an exponential pulse-charge distribution Less favourable than the reasonable peak found in a charged beam.



0

20

40

60

80

100

120

0 5 10 15 20 25 30 35

X-Ray Anode Current (mA)

Co

un

tin

g r

ate

(kH

z cm

-2)

2500 2600 2700 Linear (2700)

Efficiency is kept up to 100 kHz/cm2.

Very encouraging…



Sigma ~ 100ps seems to be kept up to 50 kHz/cm2

0

50

100

150

200

250

0 10 20 30 40 50 60

Counting rate (kHz/cm2)

Tim

ing

res

olu

tio

n (

ps)

Sigma from fitFWHM/2.362700-2900 V2500-2600 V

RandomCoincid.

Signal

But background of random coincidences fit with gaussian + symmetric exponentialHow does it affect the measurement of the real sigma? visit Rosendorf…

CBM goalwell in reach


Rate / Temperature Presented last meeting by D.Gonzalez


Rate / Temperature

Beam test in November

When run warm (~50ºC) may comfortably reach a few 1000 Hz/cm2

Geometric acceptance ≈ 87 %

Extrapolated from beam-tests on the previous HADES prototype, assuming a 25ºC temperature increase

0

75ºC=CBM goal…


Rate / Temperature

Test bench with 25 elements

Heating and sensing element

20 W heater

Hardware temperature limiter

1-WIRE® interface + power

Thermometer

Distributed temperature control system (in development)

Reasonablecabling.

Present accuracy~1 ºC.


RPC layout optionsSingle cell chambersShielded timing RPCsMultistrip counter


Single cell chambers

Coincides with the semiconducting glass

effort


Shielded timing RPCs

Actual parts, industrially produced.

Uniformity tests with 22Na (positron) source

Crosstalk for avalanches is below the noise level

50

70

90

110

130

150

170

-600 -400 -200 0 200 400 600

Position (ps)

Tim

e r

es

olu

tio

n (

ps

)

Uncorrected Charge-corrected

49500

49550

49600

49650

49700

49750

49800

-600 -400 -200 0 200 400 600

Position (ps)

Mea

n T

ime

(ps

)

Beam test in November

Final prototype of the HADES RPC-TOF wall

Designed to run warm (up to 60ºC)


Multistrip counters (FOPI)

Present design: 8 gaps

Very puregaussiandistribution


Multistrip countersSingle hit Double hit

1kHz/cm2

100Hz/cm2


RPC electronicsPreamplifier/discriminatorFOPI-RPC electronicsTime measurement and digital backend


Preamplifier / discriminator

Performance of the existingfront-end based on a multichip design

Likely, for CBM an integrated design will be needed


FOPI-RPC electronics

TAQUILA system resolution of 33 ps demonstrated

Possible conceptfor CBM


Conclusion

Many developments and studies are under way in key aspects likeAgingPhysics simulationRate capabilitySystem layoutTest facilitiesTheoretical understanding

Some significant progress has been made.Further results from beam tests expected later this year.

development of timing rpcs presented by p.fonte for the tof-rpc group

Documents

tofrpc aging

tofrpc hv

tofrpc group slide

tofrpc improvement

cbm meeting

tofrpc test facility

tof plane slide

tofrpc physics simulation