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Evgeny Maev Aging Workshop at DESY 2001
Study of aging properties of the wire chamber, operating with
high-pressure hydrogen, designed for a precision measurement of the
µp-capture rate.
V. Andreev1, A. Fetisov1, V. Ganzha1, G. Gavrilov1, A. Krivchitch1,E. Kuznetsova1, V. Lebedev1, E. Maev1, O. Maev1, C. Petitjean2, G. Petrov1,
G. Schapkin1, G. Semenchuk1, L. Schipunov1, A. Vorobyov1
1Petersburg Nuclear Physics Institute (PNPI), Gatchina 188350, Russia2Paul Scherrer Institute, PSI, CH-5232 Villigen PSI, Switzerland
ABSTRACT
The project for high precision studies of the muon capture in hydrogen isbased on application of a multi-wire proportional chambers (MWPC) operatingin ultra pure deuterium-depleted hydrogen (protium) at high pressure. A spe-cial test setup was constructed at PNPI to investigate the MWPC performanceat the expected experimental conditions. The chambers were tested inside ofthe vessel filled with a clean hydrogen at 10 bar pressure. The aging studies ofthe MWPCs were performed under intense irradiation from the alpha-source(Am241) and beta-source (Sr90). For example, after 45 days of continuousirradiation by alpha-particles with four intermediate gas refillings we did notsee any changes in the currents,in the signal shapes, and in the counting rates.It was demonstrated that the MWPCs can operate without degradation atleast up to accumulated charges of 0.1 C/cm.wire. These irradiation conditionsare much more severe than in the real experiment. The electron microscopicand X-ray analysis of the anode and cathode wires revealed no serious signsof destruction of the wire surfaces. However, in several radiation tests anappearance of the dark currents was observed (up to 10mkA), the nature ofwhich is not yet clearly understood. During the study of the MWPC we haveobserved the appearance of short duration signals with the amplitudes anorder of magnitude larger than of normal signals from the alpha-particles. Thenumber of such signals (”streamers”) strongly depends on HV. We shall con-tinue these tests in the future with the goal to obtain more detail informationabout aging properties of the MWPCs, operating with high-pressure hydrogen.
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Evgeny Maev Aging Workshop at DESY 2001
The test setup for studies of MWPCs and TPCs in hydrogen.
H2
PA2
PA1
PA3
PA4
PA5
PA6
PA7
PA8
PA9
PC2
PC1
cathode
filter
filter
filter HV2
HV1
HV3
PA1,3
PA2
PA4-9A.D.4-9
pump
A.D.2
A.D.1,3
Sr90
A.D.7
A.D.6
A.D.5
A.D.4
A.D.3
A.D.2
A.D.1
A.D.9
A.D.8
FADC1
FADC6
FADC5
FADC4
FADC3
FADC2
FADC6
FADC5
FADC4
FADC3
FADC2
FADC1
A.D.9
A.D.4
A.D.5
A.D.6
A.D.7
A.D.8
&
P.U.
1
C.U.
CAMAC
TRSTTINH
ORCLR
RQ
IN/OOUT
IN
CRATE
CONTR.PC
FCLR
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Evgeny Maev Aging Workshop at DESY 2001
0
1000
2000
3000
4000
5000
6000
7000
8000
6.8 6.9 7 7.1 7.2
HV, kV
Gas
gai
n
electronsα-particles
Gas gain vs HV. Measurement with the MWPC operating in
10 bar hydrogen gas irradiated by α- and β-sources. The basic
parameters of MWPC are:
Anode wire plane: W(Au) wires, diameter 25 µm, 2mm wire spacing.
Cathode wire plane: Fe wires, diameter 50 µm, 0.5mm wire spacing.
Anode-cathode gaps: 2.5 mm
The MWPC’s showed stable operation up to HV=7.2 kV
(E=900 kV/cm on the surface of the anode wire) providing the
effective gas gain up to 2·103 and 8·103 while detecting α-particles
and relativistic electrons, respectively. The difference in gas gains
between α and β-particles is due to the space charge effect.
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Evgeny Maev Aging Workshop at DESY 2001
0 1000 2000 3000 4000 5000 6000 7000
100
101
102
103
104
HV, V
Gai
n
ionization region
proportional region
Gas gain vs HV. Measurement with the MWPC operating in 10
bar hydrogen gas irradiated by α-source. The basic parameters
of MWPC are:
Anode wire plane: W(Au) wires, diameter 25 µm, 4mm wire spacing.
Cathode wire plane: Fe wires, diameter 50 µm, 1mm wire spacing.
Anode-cathode gaps: 3.5 mm
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Evgeny Maev Aging Workshop at DESY 2001
t6
t5
t4
t3
t2
t1
6 anode
2 anode
3 anode
4 anode
5 anode
1 anode
12
8
4
16
8
32
16
32
16
16
16
8
8
140100 120 160 180 200
Time ( 1 ch = 10 ns )
Sequence of signals from FADC created by a β-particle from Sr90
crossing TPC nearly parallel to the anode plane.
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Evgeny Maev Aging Workshop at DESY 2001
0
20
40
60
80
100
010
2030
4050
60700
10
20
30
40
50
60
70
80
90
100
events = 9781
Width, 1ch=10ns
Ageing test of the PC with α−source, anode=all, HV=5.9kV, events=10000 5.09.2000
Amplitude, channels
Nevents
The amplitude-width correlation of the signals from α-source (Am241)
at HV=5.9kV.
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Evgeny Maev Aging Workshop at DESY 2001
0
20
40
60
80
100
010
2030
4050
60700
5
10
15
20
25
30
35
40
events = 9853
Width, 1ch=10ns
Ageing test of the PC with α−source, anode=all, HV=6.5kV(d), events=10000 6.09.2000
Amplitude, channels
Nevents
The amplitude-width correlation of the signals from α-source (Am241)
at HV=6.5kV.
During the studying of MWPC was observed the appearance of short
width signals ”streamers” (left region) with amplitude larger then nor-
mal signals of α-particles (right region). Their intensity strongly de-
pends on HV. Below 6 kV they are absent, and at 7 kV they contribute
∼ 50% of the total number.
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Evgeny Maev Aging Workshop at DESY 2001
6 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 6.9 70
5
10
15
20
25
30
35
40
45
50
55 Ageing test of the PC with α−source
Yield of "streamers", %
V, kV
Intensity of the ”streamer” signals vs HV.
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Evgeny Maev Aging Workshop at DESY 2001
Prototype of the detector for µCAP experiment.
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S1 S2 S3
Prototype of the µp-capture detector was designed and tested
in a muon beam at PSI. It consisted of two muon beam MWPCs
the TPC, and four planes of electron MWPCs located above the
TPC. The anode wires in the detection plane were oriented in
the X-direction (75 wires). The wires in the strip plane oriented
along the Z-direction were joint in 4 mm strips to detect the X-
coordinate of the stopped muon (38 strips). The 3 coordinates of
the muon stop were measured with the resolution of ± 1 mm (Y),
± 2 mm (X) and ± 2 mm (Z). This device is designed to select
clean muon stops in 3D space and also to measure the muon decay
electron trajectory.
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Evgeny Maev Aging Workshop at DESY 2001
strips
anodes
cathode
grid
µ
This figure shows a schematic view of the time projection cham-
ber (TPC). The TPC contains four wire planes. The drift space
between the cathode and the grid planes is 12 cm. The ioniza-
tion electrons are driven through the grid plane to the anode wire
plane, and create avalanches around the anode wires. The sig-
nals are detected from the anode wires and also from the cathode
strips (groups of wires) in the strip plane.
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Evgeny Maev Aging Workshop at DESY 2001
0 50 100 150 200 250 300 350 4000
50
100
150
200
250
300
Am
plit
ud
e, A
+20
× (N
a−1)
Time, channel=40ns
Nan
od
e
µ − e
12
11
10
9
8
7
6
5
4
3
2
1
The signals on TPC anode wires from µ-e decay event. The muon
can be seen stopping in the region of anode 4. The decay electron is
seen on anodes 4-12 going to the upper left.
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Evgeny Maev Aging Workshop at DESY 2001
Stereoview of the final setup for µCAP experiment (scintillator array,
wire chambers and TPC vessel).
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Evgeny Maev Aging Workshop at DESY 2001
Stereoview of TPC of the final setup for µCAP experiment.