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First results from tests of
gaseous detectors assembled
from resistive meshes
P. Martinengo1, E. Nappi2, R. Oliveira1, V. Peskov1,
F. Pietropaola3, P. Picchi4
1CERN,
Geneva, Switzerland
Bari, Bari, Italy
3 INFN Padova, Padova, Italy
4NFN Frascati, Frascati, Italy
2INFN
Why not combining RPC and Micromegas
For large Micromegas (not segmented) discharge can be a problem for
electronics. This can be avoided by adopting the RPC principle
1- Resistive anode
2- Resistive mesh : few M Ω.cm Kapton
holes made with LASER
(collaboration with Rui)
cathode
Resistive mesh
Anode
I.Laktineh, IPN-Lyon, Rpeort at the November 2009 RD51meeting
Preliminary
Signal obtained from the mesh: Pream ORTEC142B+AMPLIFIER(gain=20)
We have ordered from Rui resistive
meshes much before the Laktineh talk,
however received it after the Laktineh talk
.. so certainly we give him and his
group all credits
Resistive Mesh Detectors
This approach could be an alternative/or
complimentary to the ongoing efforts in developing
MICROMEGAS and GEMs with resistive anode
readout plates and can be especially beneficial in the
case of micropattern detectors combined with a
micropixel-type integrated front end electronics.
Mesh #1 had a thickness t= 20μm, hole’s diameter d=70 μm and hole spacing a=140 μm, resistivity –a few MΩ/□
it was made from resistive Kapton by a laser drilling technique
From these stretched meshes different detectors could be assembled:
Drift mesh
a)
c)
Resistive mesh
Spacers
Amplifier
GEM,
PPAC,
G=0.05-0.1mm
G=1-3mm
b)
d)
MICROMEGAS,
G=-0.1-0.3mm
GEM,G=0.2mm+
MICROMEGAS
G=0.01-0.3mm
3 mm gap RPC: mesh #2 had t=25 μm, d=0.7 mm and a=1.7 mm; mesh #3
had t=25 μm , d=0.8 mm, a=2.8mm;
Meshed # 2 and #3 were manufactured by usual mechanical drilling techniques.
View from the bottom
Resitsive anode
Readout strips
Some results obtained with large gap resistive
mesh RPC
Gain
RM-RPC, G=3mm
Resistive RPC
Cathode-mesh: t=25 μm,
1.00E+04
1.00E+03
1.00E+02
1.00E+01
1.00E+00
1.00E-01
d=0.7 mm and a=1.7 mm
0
1000
2000
3000
4000
5000
Anode –resistive Kapton
Cathode –anode gap
3mm
Voltage (V)
Large-gap mesh RPCs were used in early experiments just to demonstrate the operational principle
Spark’s energy was suppresses on orders of magnitude
(For the details of measurement see :A. Di Mauro et al., arXiv:0706.0102, 2007 )
In fact it is an RPC with a drift region!
Some results obtained with the resistive mesh#1
Gain
RM-RPC,G=1mm
1.00E+05
1.00E+04
1.00E+03
1.00E+02
1.00E+01
1.00E+00
1.00E-01
Resistive MICROMEGAS
Cathode-mesh (t= 20μm, d=70 μm ,
Ar+8%CH4
a=140 μm)
Ne+8%CH4
0
500
Anode –metallic
Cathode –anode gap 1mm
1000 1500 2000 2500 3000
Voltage (V)
Max available rate
with our 55Fe
With alphas we almost
reached the Raether limit,
with 55F we were 10 times below it
indicating that at high voltages
breakdowns were due to imperfections
Signal amplitude (arb. units)
Triangles-alphas, squares-55Fe
1.2
1
0.8
55Fe
0.6
0.4
0.2
0
1
10
100
Rate (Hz/cm2)
1000
10000
RM-mM, G=0.1mm, Ar+10%CH4
Gain
1000
Resistive MICROMEGAS
Cathode-mesh (t= 20μm, d=70 μm ,
Preliminary!
100
a=140 μm)
Anode –metallic or resistive Kapton
Cathode –anode gap 0.1mm
Fishing line and Kapton spacers
10
Kapton spacers
1
0
200
400
600
Voltage (V)
Triangles-alphas, squares-55Fe
RM-mM, G=0.2mm, Ar+15%CO2
1000
Preliminary!
The same tendency as with a 1mm gap
detectors: the Raether limit is reached
with alphas, but not with 55Fe
(due to even stronger contribution of
imperfections at this very small gap)
Gain
100
10
Kapton spacers
1
0
200
400
600
800
Voltage (V)
Triangles-alphas, squares-55Fe
1000
Resistive GEM:
Two parallel meshes (t= 20μm, d=70 μm ,
Drift
a=140 μm)
Gap =0.05mm
Fishing lines and Kapton spacers
RM-GEM
RM-GEM, G=0.05mm Ar+20% CO2
The maximum achievable gain for
the resistive GEM was low,
probably due to the mesh and
design defect
Gain
100
Preliminary!
10
Kapton spacers
1
0
100
200
300
400
Voltage (V)
Triangles-alphas, no signals were observed with 55Fe
Cascaded resistive mesh detectors
Drift
Resistive GEMs in cascade:
Two parallel meshes (t= 20μm, d=70 μm ,
a=140 μm)
Gaps =0.2mm, fishing line spacers
RM-GEM
Ar+15%CO2
RM-μM
10000
Preliminary!
Voltage drop over RM-GEM 700V,
transfer field 1.5kV/cm
Gain
1000
RM-mM+RM-GEM
(Cascaded)
100
RM-mM
Single
10
1
Raether limit is reached with55Fe!
0
200
400
600
Voltage(V)
Triangles-alphas, squares-55Fe
800
1000
Preliminary conclusion:
resistive meshes are ideal for multistep
designs:
Higher gains
No discharge propagation (the main enemy in
cascaded metallic GEMs)
Potentially good position resolution
Position resolution:
CsI
Pulse profile
It is already 2-3 times better that was
obtained with a RETGEM.
We are quite confident that a much better
position resolution can be achieved with
a finer mesh and with more accurate
measurements and work in this direction
is now in progress.
Signal amplitude (V)
1.4
Preliminary!
1.2
1
0.8
~300um
0.6
0.4
0.2
0
0
1
2
3
4
Strip grpou number
5
6
7
Conclusions.
● Resistive meshes developed and tested in this work are convenient
construction blocks for various spark-protective detectors including the
GEM-like and MICROMEGAS-like.
● Due to the small diameter of their holes and the fine pitch, a better
position resolution can be achieved with resistive mesh –based detectors
than with the RETGEMs.
● No discharge propagation was observed in our experiment when RMDs
operated in cascade mode. One of the advantages of the cascade mode is
the possibility to reduce an ion back flow to the cathode which can be an
attractive features for some applications such as photodectors or TPC.
● Our nearest efforts will be focused on developments and tests of fine
pitch meshes manufactured by various techniques and on optimization its
geometry and resistivity. This will allow for the building of high position
resolution spark protected micropattern detectors. One of the possibilities
is to use the fine resistive mesh for MICROMGAS combined with a
micropixel readout plate; this approach can be an alternative to current
efforts from various groups to develop micropixel anode plate with resistive
spark protective coating