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D. González-Díaz, A. Mangiarotti and P. Fonte. Primary statistics Multiplication process [A....
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Transcript of D. González-Díaz, A. Mangiarotti and P. Fonte. Primary statistics Multiplication process [A....
D. González-Díaz, A. Mangiarotti and P. Fonte
)'2('1
')( )(
01)(0
)exp()(
'0
0
th
th
thth
enIen
e
e
nn
))1(log('0 effn
driftvS
Primary statistics
Multiplication process
[A. Mangiarotti, P. Fonte, A. Gobbi NIM A 533(2004)16]σ τ(
n 0’)
[1/s
uni
ts]
n0’
Ineff [%]
tS
gapE
Et rmsdE
dS
SdE
d
Srms
Srms
2
2
22
22 11
Intrinsic time resolution Fluctuations in the field Drop in the field
[ A. Blanco et al. NIM A 535 (2004) 272 ]
rmsE /E
σ τ(n 0’
) [1
/s u
nits
]
DATA SET
•Date: April-2003.•Place: HADES, GSI•Physical conditions: Ionizing particles from CC collisions at 1 GeV A.•Detector:
0.3 mm 4-gap RPC (Al-Glass-Al-Glass-Al)Mixture: Freon/Iso-butan/SF6 (98.5/0.5/1)HV: 3.1-3.4 kV/gapRates: 0.1-1.5 kHz/cm2
H. Alvarez-Pol et al, NIM A 533(2004)79 and 535(2004)277
OBSERVABLES NEEDED:
Mainly the total charge and the rms of the total charge. They are directly
related to the fluctuations of the field:
)](,[2 QrmsQE
rRAQVVgap
Fluctuations in the field
Drop in the field
and to the drop in the field:
As the gas mixture was slightly different from the standard one, it will
help that S=α Vd can also be obtained independently from data.
HV = 3.1 kV/gapHV = 3.2 kV/gapHV = 3.3 kV/gapHV = 3.4 kV/gap
OBSERVABLES AVAILABLE:
How to go from the available to the needed?: [ the usual problem!! ]
)(
)'/log()( 0
0gap
tgap VS
nmVt
glassgap VVV
)( Tgap VVcq
gapbVSS 0
Time delay
Field in the gap
Behavior in strong space-charge regime
Linear increase with voltage
)exp(1
995.0)(
K
VVVeff
refgapgap
Accurate description of the efficiency trend
with HV for this kind of detector
[P.Fonte, V.Peskov, NIMA 477(2002)17 G. Carboni et al. , NIMA 498(2003)135]
[G.Aielli, NIMA 456(2000)82]
[A. Blanco et al. IEEE Trans. Nucl. Sci.48(2001)1249 and C. Lippmann (Thesis)]
rRAqIRVglass Ohmic drop in the glass
OBSERVABLES AVAILABLE->OBSERVABLES NEEDED [result]
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’]
CONCLUSIONS:
- A first (indirect) confirmation of the validity of the proposed modelfor describing rate effects on the time resolution of an RPC is shown.
- Better comparison requires:* Direct measurement of the total charge as a function of the rate together with its rms. * At least a factor 4 larger files. [The expected improvementof sigma with voltage is 5ps/100V-> Hard to see!].* Independent MC cross-check.
HV = 3.2 kV/gapHV = 3.3 kV/gap