diego gonzalez diaz university of santiago de compostela itep ihep (protvino), itep (moscow), inr...
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Diego Gonzalez Diaz University of Santiago de CompostelaITEP
IHEP (Protvino), ITEP (Moscow), INR (Moscow), LIP(Coimbra), USC(Santiago de Compostela)
Diego Gonzalez Diaz University of Santiago de Compostela
Diego González Díaz
(Santiago de Compostela-Spain)
A. Blanco, P. Fonte, L. Lopes, R. Ferreira-Marques
(LIP-Coimbra)
Diego Gonzalez Diaz University of Santiago de Compostela
Detector used for tests
- Gas mixture:
80% C2H2F4 + 20% SF6 .
- Normal window glass, 2 mm thick.
- 4-gaps, 0.3 mm thick.
- Aluminum electrodes, 2 mm thick.
- Shielding boxes.
- BGA2712 amplifier.
- Reference BICRON scintillator (110 ps for gammas).
Diego Gonzalez Diaz University of Santiago de Compostela
Sources used for tests
Na22 (~ 0.1 mCi) (mainly used for calibration)Na22 (~ 1 mCi)Co60 (~ 1 mCi)
2222
2222
*
*
NeNe
eNeNa e 2 x 0.511 MeV collinear (positron annihilation)
1.274 MeV
5959
5960
*
*
CoCo
eCoCo e1.173 MeV, 1.332 MeV (opposite directions but not perfectly collinear)
Interaction occurs through Compton scattering in the electrodes. The electron scattered ionizes the gas and is detected. Charge distribution is different than for MIPS.
q
qq ped
eqdq
dN)(
1
Diego Gonzalez Diaz University of Santiago de Compostela
Trigger system used for tests
Efficiency trigger Time resolution trigger
source
20
/12
1
Lx
N
Ldx
dN
L
RPC
self-trigger mode
source
RPC
Coincidence with a 110 ps scintillator
scintillator
Due to the high rate environment, coincidences by chance are dominant and must be suppressed with adecuate cuts.
Diego Gonzalez Diaz University of Santiago de Compostela
)(
)(
TT
1
00
))(
)(()(
T
T
TR
TRT
‘Rate capability’: If the rate capability κ(T) increasesa factor n, the rate can be increased by the samefactor and the performance of the detectorremains unaltered.
oT
TVV *As a first approach, if the
reduced high voltage V* is kept constant
Temperature dependence
deg6
2)(
T
Diego Gonzalez Diaz University of Santiago de Compostela
Time resolution measurements
Time resolution for gammas stands
within 90 ps without significative
dependence on primary rate. So it is
hard to get the κ(T) factor from
timing
measurements.
No signific
ative dependence
[!]
Diego Gonzalez Diaz University of Santiago de Compostela
Efficiency measurements
Na22
Na22 + Co60
Na22 + Co60
(2.5 cm further)
Diego Gonzalez Diaz University of Santiago de Compostela
Efficiency measurements
1
00
))(
)(()(
T
T
TR
TRT
X12
)(Td
e
Increasing T
33 degrees
Diego Gonzalez Diaz University of Santiago de Compostela
Geometric acceptance ≈ 87 %
2
2
/100%5.1
/1007.467
cmHz
cmHzpspsT
Results in Carbon 2GeV/A beam tests, for the same detector. April 2003
Conclusions (I)
T~20 degrees
Diego Gonzalez Diaz University of Santiago de Compostela
2
2
/100)(
%5.1
/100)(
7.467
cmHzTK
cmHzTK
pspsT
When the Temperature increases??
1
00
))(
)(()(
T
T
TR
TRT
Rate capability
deg6
2)(
T
deg9
2)(
T
measured expected Under study!
Conclusions (II)
Diego Gonzalez Diaz University of Santiago de Compostela
Geometric acceptance ≈ 87 %
for κ(T) measured in 30 degrees increase
Conclusions (III)
Diego Gonzalez Diaz University of Santiago de Compostela
App1: Ageing
T increase of 30 degrees