Transcript INSTR2008

Two-phase Ar avalanche detectors
based on GEMs
Budker Institute of Nuclear Physics, Novosibirsk
A. Bondar, A. Buzulutskov, A. Grebenuk,
D. Pavlyuchenko, Y. Tikhonov
Outline
- Motivation: coherent neutrino-nucleus scattering, dark matter
search, solar neutrino detection
- Two-phase Ar avalanche detector without CsI PC
- Two-phase Ar avalanche detector with CsI PC
- Summary
1
Motivation: cryogenic detectors for coherent neutrino
scattering, dark matter and solar neutrino detection
Two-phase Ar
detector for
dark matter
search
WARP
Collaboration
[P. Benetti
et al., Astroparticle
physics,
28(6)(2008)
495]
Two-phase Ar detectors for
dark matter search using
thick GEM readout
A. Rubbia et al.,
J.Phys.Conf.Ser.39(2006)129
Two-phase Ar detector for
coherent neutrino-nucleus
scattering
Hagmann & Bernstein, IEEE
Trans. Nucl. Sci. 51(2004)2151;
Two-phase He or Ne detectors
for solar neutrino detection
using charge readout
Columbia Univ (Nevis Lab) & BNL,
www.nevis.columbia.edu/~ebubble
2
Principles of two-phase avalanche detectors based on GEMs
- Primary ionization (and scintillation) signal is weak: of the order of 1, 10, 100 and 500 keV
for coherent neutrino, dark matter, solar neutrino and PET respectively
 Signal amplification, namely electron avalanching in pure noble gases at cryogenic
temperatures is needed
- Detection of both ionization and scintillation signals in liquid might be desirable, the
latter to provide fast signal coincidences in PET and to reject background in neutrino and
dark matter detection
The concept of two-phase (liquid-gas) or high
pressure cryogenic avalanche detector using
multi-GEM multiplier, with CsI photocathode on
top of first GEM
1. Buzulutskov et al., First results from cryogenic avalanche
detectors based on GEMs, IEEE Trans. Nucl. Sci. 50(2003)2491
2. Bondar et al., Cryogenic avalanche detectors based on GEMs,
NIM A 524(2004)130.
3. Bondar et al., Further studies of two-phase Kr detectors based
on GEMs, NIM A 548(2005)439.
4. Buzulutskov et al., GEM operation in He and Ne at low T, NIM A
548(2005)487.
5. Bondar et al., Two-phase Ar and Xe avalanche detectors based
on GEMs, NIM A 556(2006)237
6. Bondar et al., A two-phase Ar avalanche detector operated in a
single electron counting mode, NIM A 574(2007)493
7. Bondar et al., First result of the two-phase argon avalanche
3
detector performance with CsI photocathode, NIM A 581(2007)
241
Two-phase avalanche detectors based on GEMs:
previous results
Unique advantage of GEMs and
other hole-type structures: high
gain operation in noble gases
-3GEM operation in noble gases at
high pressures at room T
Budker Inst: NIM A 493(2002)8;
494(2002)148
Coimbra & Weizmann Inst:
NIM A 535(2004)341
Stable 3GEM
operation in two-phase
mode
-In Ar: rather high gains
are reached, of the order
of 104,
-In Kr and Xe: moderate
gains are reached,
about 103 and 200
respectively
Bondar et al., Two-phase Ar
and Xe avalanche detectors
based on GEMs,
NIM A 556(2006)237
Successful operation of the
two-phase Ar avalanche
detector in single electron
counting mode
-Pulse-height spectra for single
and 1.4 electron at gain 4·104 ,
in 3GEM.
-Single and two electron events
would be well distinguished
by spectra slopes
Bondar et al, NIM A 574(2007)
493
4
Two-phase Ar avalanche detector: experimental setup
- Developed at Budker Institute
- 2.5 l cryogenic chamber
- Operated in Ar with liquid thickness 10 mm
- Liquid purity: electron lifetime larger than 3 s
( drift length 1cm)
- 3GEM ( active area 33cm2 ) assembly inside
- Irradiated with pulsed X-rays, -particles, rays and neutrons
1.45
Ar
Cathode gap
open: cooling
solid: heating
1.40
Capacitance (pF)
1.35
1.30
1.25
1.20
Cathode gap
capacitance as a
function of
pressure in Ar
during coolingheating
procedures
1.15
1.10
0.8
Two-phase
mode
1.0
1.2
1.4
Pressure (atm)
1.6
1.8
Gaseous mode
5
Two-phase Ar avalanche detector: experimental setup
2.5 liter cryogenic chamber
5 cm
HV Feedthrough
Heat
Exchanger
LN2
GAr
GN2
Cu shield
3GEM
Vacuum
jacket
Blowup
GEM3
GEM2
X-ray windows
GEM1
GAr
LAr
-e
Cathode
Grid
e, neutrons
6
Two-phase Ar avalanche detector: emission and gain
characteristics
Electron emission
through liquid/gas
interface
Gain characteristics
Ionization source: pulsed X-ray tube
500
10
Two-phase Ar
84K, 0.70atm
CsI/GEM1
5mm LAr
Pulsed X-rays
Calibration signal
Shaping time 10s
300
Gain
Pulse-height (mV)
400
200
100
5
10
4
10
3
10
2
10
1
10
0
31/08/06
Two-phase Ar, 3GEM
84K, 0.70atm
1.0cm LAr
Pure LAr
14/09/06
28/12/06
CsI/3GEM
31/08/06
3GEM+PCB
0
0
1
2
3
4
ELAr (kV/cm)
– Anode pulse-height as a function of electric
field in the liquid induced by pulsed X-ray
-Extraction is saturated
at lower fields compare to Kr and Xe
250
300
350
400
450
500
 VGEM ( V )
- Maximum reached gain 14·103
- Gain characteristic is well reproducible
7
Two-phase Ar avalanche detector: energy spectra for
different radioactive sources
X-rays from
511keV -rays from
241Am
22Na
600
Two-phase Ar, 3GEM
84K, 0.70atm
241
Am -rays
Gain ~ 3800
E(LAr) = 1.71 kV/cm
Shaping time 10s
10
3
10
Counts
Counts
400
<E>(outside pedestal) = 131 keV
4
Two-phase Ar, 3GEM
84K, 0.70atm
22
Na -rays
Gain ~ 500
E(LAr) = 1.71 kV/cm
Shaping time 10s
- 60 keV X-ray peak from
241Am was used to calibrate
energy scale
511keV -ray
photoelectric peak
2
10
200
1
10
0
0
0
20
40
60
80
100
120
Energy (keV)
-particles from
90Sr
10
0
100
200
Compton edge
300
400
Energy (keV)
500
600
1000
<E> = 450 keV
<E>(for>190keV) = 620 keV
800
Counts
600
Two-phase Ar, 3GEM
84K, 0.70atm
90
Sr -particles
Gain ~ 380
E(LAr) = 1.71 kV/cm
Shaping time 10s
- Only a fraction of -particle energy was
deposited in cathode gap due to 5mm
dead zone between chamber
bottom and cathode
-<E> (for > 190keV) = 600keV
400
200
0
0
200
400
600
800
1000
Energy (keV)
1200
1400
1600
8
Two-phase Ar avalanche detector: purity effect and
energy resolution for 241Am 60 keV X-ray peak
LAr purity: experiment
250
200
1st purification
cycle
Two-phase Ar, 3GEM
84K, 0.70atm, 1.0cm LAr
241
Amrays
VGEM = 449V, Gain ~ 8500
ELAr= 1.52 kV/cm
Counts
150
2nd purification
cycle
- Several purification
cycles are enough to
3000
achieve electron
lifetime in liquid Ar
larger than 3s ( 1cm )
100
Energy resolution
60 keV X-rays
ELAr= 0.76 kV/cm
Two-phase Ar, 3GEM
84K, 0.70atm, 1.0cm LAr
241
Amrays
VGEM = 432V, Gain ~ 3700
2000
ELAr= 1.52 kV/cm
/E = 0.37/2.15=17%
Counts
50
0
0
1
2
3
4
5
6
Pulse-height (V)
7
8
9
10
1000
LAr purity: Monte Carlo
150
- Shape and position
0
1
2
3
4
of 60 keV X-ray
Pulse-height (V)
peak depends on
liquid purity
- Two-phase Ar, 3 GEM, 60 keV X-rays from 241Am,
gain ~ 4000
Simulation
1.0cm LAr
60 keV rays
Electron drift
path 1cm
No electron
attachment
Counts
100
- Effect of extraction field is well pronounced
50
- Energy resolution is 17%
0
0
1
2
3
4
5
6
Pulse-height (V)
7
8
9
10
9
Two-phase Ar avalanche detector:
detection events with small energy deposition
10
5
Two-phase Ar, 3GEM, 84K, 0.70atm, 1.0cm LAr
Counts (arb. scale)
241
10
4
10
3
10
2
10
1
252
Cf: n+
2.4cm Pb screen
Gain~4800
ELAr= 1.5 kV/cm
Am: 60 keV Xrays
Gain~4800
ELAr= 1.5 kV/cm
Single
electrons
Gain~4200
ELAr= -0.4kV/cm
0
10
0.01
0.1
1
Pulse-height (V)
Pulse-height spectra at gain ~
4500 for:
- Single electrons
- 252Cf neutrons and -rays
- 241Am 60 keV X-rays
10
Nuclear recoils due
to neutron-nucleus elastic scattering
Energy spectra at gain ~ 4500
- Detector is irradiated with neutrons and
-rays from 252Cf, 22Na through the 2.4cm Pb
shield
-60 keV X-ray peak from 241Am was used to
calibrate energy scale
10
Two-phase Ar avalanche detector: avalanching stability
4
0.74
3
60 keV Peak Position (V)
60 keV peak position (V)
solid: peak position
open: pressure
2
Two-phase Ar, 3GEM
84K, 0.70atm
241
1.0cm LAr, Am -rays
VGEM = 432V
1
0.73
3
0.72
Two-phase Ar, 3GEM
84 K, 1.0cm LAr
241
Am -rays
VGEM = 432V
2
0.71
E(LAr) =1.5kV/cm
Gain ~ 1500-4500
0.70
1
0.69
E(LAr) = 1.5kV/cm
Gain ~ 1500-4500
0
0
0
2
4
6
8
10
12
14
16
18
20
22
Time (hours)
- Relatively stable operation 3GEM during
20 hours in two-phase Ar at
gain ~1500-4500
24
0.68
0
1
2
3
4
5
6
Time (hours)
- Correlation between pressure and peak
position (gain) is clearly seen
Operation of two-phase Ar avalanche detector is rather stable
11
Pressure (atm)
4
Two-phase Ar avalanche detector with CsI PC:
experimental setup
- GEM1 with CsI photocathode (PC)
- QE of CsI PC = 5% at 185nm
-The scintillation-induced photoelectrons released at the
CsI photocathode are collected into the GEM holes and
then multiplied, producing a so-called “S1” signal.
The ionization-induced electrons are detected after some
time, needed for drifting in the liquid and gas gaps and
for emission through the liquid-gas interface; they
produce a “S2” signal, delayed with respect to S1.
S2 Gain ~ 5400
E(LAr)=0.25kV/cm
Shaping time 0.5 s
S1
- Anode signals induced by -particles from 90Sr in
12
two-phase Ar avalanche detector with CsI photocathode
Two-phase Ar avalanche detector with CsI PC:
-particles from 90Sr
Anode signal, averaged over
~ 100 events of a S1+S2
type, at different drift
fields in LAr
0.4
Two-phase Ar, 3GEM
84K, 0.70atm
90
Sr -particles
Gain ~ 2500
E(LAr) = 0.25kV/cm
Shaping time 0.5s
111 events averaged
Pulse-height (V)
0.3
0.2
0.1
0.0
-10
0
10
20
Time (s)
Peak delay spectra of S1 signal
with respect to S2 signal for
1.0
different drift fields in LAr
40
Two-phase Ar, 3GEM
84K, 0.70atm
90
Sr -particles
Gain ~ 2500
E(LAr) = 0.61kV/cm
Shaping time 0.5s
100 events averaged
0.8
Pulse-height
- The signals are induced by 90Sr
-particles in LAr, at gain ~ 2500,
shaping time 0.5s
- Shaded spectrum corresponds
to low drift field in LAr
- Time delay between S1 and S2
depends on the drift field and is
larger for lower fields
-This confirms that S1 is induced by
primary scintillation signal
30
- Observation both S1 and S2
signals at lower drift field
0.25kV/cm and small shaping time
0.5s
-Such conditions were necessary
to have enough time delay
between S1 and S2; otherwise
they would overlap
0.6
0.4
0.2
0.0
-10
0
10
20
Time
30
40
13
Two-phase Ar avalanche detector with CsI PC:
-particles from 90Sr
2000
S2 alone
S2 amplitude (electrons)
Distribution of events in the
plane S2 vs. S1 amplitudes
Two-phase Ar, 3GEM
84K, 0.70atm
90
Sr -particles
Gain ~ 2500
E(LAr) = 0.25kV/cm
Shaping time 0.5s
1500
- At gain ~ 2500, drift field
E(LAr) = 0.25kV/cm, shaping time 0.5s
- Most events are of the “S1+S2” type
where S1 & S2 are observed and correlated
to each other
1000
S1+S2
S2 treated as S1
500
0
0
20
40
60
80
100
120
140
S1 amplitude (photoelectrons)
14
Two-phase Ar avalanche detector with CsI PC:
-particles from 90Sr
NPE or NE
1
10
100
1000
10000
200
Counts (arb. scale)
150
Two-phase Ar, 3GEM
84K, 0.70atm
Gain ~ 2500
Shaping time 0.5s
90
Sr -particles
E(LAr) = 0.25kV/cm
S2
90
100
Sr -particles
E(LAr)=0.25kV/cm
S1
241
Am -rays
E(LAr)=
=1.71kV/cm
S2
50
0
0.01
0.1
1
10
Amplitude spectra of S1 and S2
- Top scale is expressed in initial charge
prior to multiplication, i.e. p.e. for S1 and
e. for S2
-S1 & S2 spectrums have a single peak
corresponding to high energy component
of the -particle spectrum
- Npe in S1 peak is about 30. This
corresponds to the detection of
scintillation light due to a deposited
energy of about 600keV.
- Photon detection efficiency = NPE /NPH ~ 10-3
accounting for the scintillation
light yield in LAr, of 40 photons/keV
100
Amplitude (rel. units)
15
Two-phase Ar avalanche detector with CsI PC:
X-rays from 241Am
Anode signals induced by
- Shaping time 0.5s
241Am
X-rays in two-phase Ar avalanche detector
Single event
- Gain ~ 14000,
E(LAr) =0.37kV/cm
- S1 is seen
- Amplitude <S1> ~ 2 p.e.
0.3
S2
Pulse-height (V)
3
Two-phase Ar, 3GEM
84K, 0.70atm
241
Am -rays
Gain ~ 6600
E(LAr) = 1.71kV/cm
Shaping time 0.5s
100 events averaged
2
0.2
0.1
S1
0.0
-10
1
0
10
20
Time (s)
30
40
Averaged over 100 event
0
-10
0
10
20
Time (s)
30
40
S2
0.20
Two-phase Ar, 3GEM
84K, 0.70atm
241
Am -rays
Gain ~ 14000
E(LAr) = 0.37kV/cm
Shaping time 0.5s
100 events averaged
0.16
- Gain ~ 6600, E(LAr) = 1.71kV/cm
- S1 does not seen
Pulse-height (V)
Pulse-height (V)
Two-phase Ar, 3GEM
84K, 0.70atm
241
Am -rays
Gain ~ 14000
E(LAr) = 0.37kV/cm
Shaping time 0.5s
S1
0.12
0.08
0.04
0.00
-10
0
10
20
Time (s)
30
40
16
Two-phase Ar avalanche detector with CsI PC:
511keV -rays from 22Na
Anode signals induced by 22Na 511 keV -rays
60
Two-phase Ar, 3GEM
84K, 0.70atm
22
Na -rays
Gain ~ 6600
E(LAr) = 0.25kV/cm
Shaping time 0.5s
Trigger BGO counter
40
Counts
- Scintillation BGO counter was used to provide
coincidence between the two -quanta
-Averaged over 100 events, shaping time 0.5 s
- E(LAr)=0.25kV/cm
- S1 is seen
S1 peak delay = 2.0s
= 0.47s
20
Trigger signal from BGO counter
0.4
0
-2
S2
Two-phase Ar, 3GEM
84K, 0.70atm
22
Na -rays
Gain ~ 6600
E(LAr) = 0.25kV/cm
Shaping time 0.5s
135 events averaged
Pulse-height (V)
0.3
0.2
-1
0
1
2
Time (s)
3
4
5
Peak delay spectrum of S1 signal
with respect to trigger signal
from BGO counter
- Gain ~ 6600, E(LAr) = 0.25kV/cm
0.1
S1
0.0
-10
0
10
20
Time (s)
30
40
17
Two-phase Ar avalanche detector: thick GEM versus
thin GEM
In this part of work we collaborate with
Weizmann Institute of Science, Israel
Thanks to Amos Breskin
Thick Gas Electron Multiplier (THGEM)
produced by the Weizmann Institute , see
THGEM (G10)
talk of A. Breskin
THGEM(KEVLAR)
Resistive Electrode Thick
GEM (RETHGEM)
produced by the CERN work-
shop
RETHGEM
- Thickness
0.4mm
0.4mm
0.4mm
- Hole diameter 0.5mm
0.3mm
0.3mm
- Pitch
0.9mm
0.7mm
0.75mm
- Both THGEMs have a rim of 0.1 mm etched around the mechanically drilled holes.
18
Two-phase Ar avalanche detector: thick GEM versus
thin GEM
Gain characteristics
Ionization source: pulsed X-ray tube
RETHGEM
GEM vs. THGEM
Two-phase Ar, 84K, 0.70atm, E(LAr)=1.8 kV/cm
4
10
Thick GEM(Kevlar)
2GEM mode
2GEM
mode
3
10
10
3
10
2
RETHGEM
Two-phase Ar
E(LAr)=1.8kV/cm
Pulsed X-rays
solid: in equilibrium
open: under warming up
Gain
Gain
Thin GEM
3GEM mode
2
10
1GEM
mode
1
10
10
10
1.48atm
91K
1
1GEM mode
1.16atm
88K
0
0.70atm
84K
Thick GEM(G10)
0
10
250
500
1000
1250
1500
1750
2000
2250
VGEM (V)
- 2THGEM in two-phase Ar have maximum
reached gain 6000 for KEVLAR and 3000 for
G10 at voltages four times higher than typical
operation voltage of thin GEM.
10
2GEM mode
-1
500
750
1000
1250
1500
1750
2000
2250
VGEM (V)
- There is no gain in double RETHGEM at
standard condition of two-phase operation.
But RETHGEM have small gain of the order 10
in non-equilibrium two-phase operation
19
of cryogenic chamber.
Two-phase Ar avalanche detector: thick GEM versus
thin GEM
Pulse-height spectra
of
THGEM(G10)
241Am
X-rays
1200
Counts
800
800
THGEM(G10), 2GEM mode
Two-phase Ar, 84K, 0.70atm
Gain~1500, Shaping time 10s
E(LAr)=1.8 kV/cm
241
Am X-rays
THGEM(Kevlar), 2GEM mode
Two-phase Ar, 84K, 0.70atm
Gain~2300, Shaping time 10s
E(LAr)=1.8 kV/cm
241
Am X-rays
600
600
Counts
1000
THGEM(KEVLAR)
/A = 18%
400
400
200
200
0
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
Pulse-height (V)
0
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
Pulse-height (V)
- Energy resolution for 60keV X-rays
is the same as for thin GEM 18%
- Spectrum is deteriorated due to charging up
THGEM(G10) could replace thin GEM
20
Summary
Two-phase Ar avalanche detector without CsI PC:
- Wide dynamical range of operation (detecting single electrons, gamma-rays and
neutrons), with good energy resolution
- Stable operation for at least one day
- Efficient detection of events with small energy deposition
- 2ThGEM(G10) operate in two-phase Ar with maximum gain 3000
Two-phase Ar avalanche detector with CsI PC:
- Stable operation of CsI photocathode for one month in the two-phase Ar
avalanche detector
- Detection of both primary scintillation and ionization signals, produced by particles, X,-rays in liquid Ar in the two-phase avalanche mode.
The results obtained are relevant in the field of lowbackground detectors
sensitive to nuclear recoils, such as those for coherent neutrino-nucleus
scattering and dark matter search experiments.
21