Setup optimization toward accurate ageing studies of
gas filled detectors
Alhussain Abuhozaa,b, S. Biswasb, U. Frankenfeldb, J. Hehnerb, C. J. Schmidtb, H.R. Schmidtc
aKing Abdulaziz City for Science and Technology(KACST), Riyadh, Saudi Arabia
bGSI Helmholtzzentrum fur Schwerionenforschung GmbH, Darmstadt, Germany
cUniversity of Tubingen, Germany
[email protected]
Motivations
The degradation of the performance or
"ageing" of gas detectors under irradiation has
been observed since the start of their use in
particle physics experiments. High luminosity
experiments like the Compressed Baryonic
Matter (CBM) at FAIR, Germany will employ
several types of gaseous detectors, since
long term (~10 years) stable operation at high
rates is essential. In general, the observed
damage depends on the amount of radiation
seen by the detector. In addition many other
factors like construction materials, gas
composition, gas quality, gas flow rate,
particle rate, and particle type play an
extremely important role
Toward accurate ageing studies
The desired high accuracy coming from:
The necessity of performing the ageing test in the
laboratory in comparable conditions with those in the real
experiment.
The short period of the test comparing with the actual
lifetime of the detector in the experiment.
Stability developments
Ageing test of Vetronit G11
Ageing test of the influence of clean fiberglass
- Vetronit G11 produced by VonRoll Holding
Ltd.- has been performed. Other ageing test
has been of contaminated G11 with sawing
liquid –Micro 3000 produced by Microjet
GmbH- which consists of alcohol and
synthetic aster.
Vetronit G11
Several improvements of the setup have been implemented to
obtain the mandatory precision:
1- Modification in detector design
Two additional outer windows have been added to act as gas
tightening windows whilst the two inner foils function as more
stable cathodes.
Accumulated
Vetronit G11
contaminated with
micro- 3000
10.2 mC/cm
8 mC/cm
Time
262 hours
140 hours
Current density
11 nA/cm
16nA/cm
Ageing
no
no
charge
Outer windows
The expected accumulated charge
~ 7.5 C/cm2 after 10 year operation.
Inner
windows
With outer
Without
outer
windows
windows
The expected accumulated charge
~ 0.4 C/cm after 10 year operation.
Gain Variation ~ 8% peak-to-peak
Gain Variation ~ 1%
peak-to-peak
Experimental setup
This study has been performed with an
apparatus consisting of two identical standard
MWPCs, a clean gas system, an outgasing
box, a Copper X-ray generator and an 55Fe Xray source. In this setup the MWPC is
continuously flushed by gas through an
outgasing box at a given flow rate, where the
box contains the construction materials under
investigation, such as glues, frames etc.
Ageing test approach
For periods of 12 mins, the ageing chamber is
being irradiated 10 mins by copper X-ray
generator, subsequently the mean position of
pulse height of 55Fe X-ray source is being
registered during 1 min each chamber. The
reference chamber is being used for accurate
normalization and to distinguish the deterioration
of the gain due to ageing (if any) from the
variation due to the ambient parameters (e.g.
pressure,
temperature,
gas
composition),.
Therefore, the data (gain, counting rate, current,
resolution, and the ambient parameters ) of both
chambers are continuously recorded.
2- Temperature dependence of Gas Flow Rate
The effect of temperature variations on the behavior of the
MFCs has been investigated.
Summary
3- Premixed gas bottle
The stability of the normalized gain has been improved to a
value better than 0.6% peak-to-peak variation.
0.2%
Studies of the ageing phenomena of gas
filled detectors are necessary
A dedicated ageing test setup is operational
in GSI DetLab
The ambient parameters (e.g. temperature,
pressure etc.) should be kept constant during
the test as much as possible and the residual
should be corrected with the reference
chamber
Many optimization tests have been
performed to achieve high accuracy ageing
test
Ageing tests are performed on clean and
contaminated Vetronit G11.
Up to 10.3 mC/cm accumulated charge, no
ageing effect has been observed from clean
G11.
Up to 8mC/cm accumulated charge, no
ageing effect has been observed from
contaminated G11.