Post on 26-Mar-2020
BEGeBEGe Detector studies updateDetector studies update
Performance and analysisPerformance and analysis
DušanDušan BudjášBudjáš • • StefanStefan Schönert • Schönert • Mikael Hult*Mikael Hult*
MPI für Kernphysik • MPI für Kernphysik • HeidelbergHeidelberg* IRMM • Geel* IRMM • Geel
MMAXAX--PPLANCKLANCK--IINSTITUTNSTITUT
FFÜÜR R KKERNPHYSIKERNPHYSIK
OutlineOutline
1.1. BEGe publicationBEGe publication
2.2. BEGe pulseBEGe pulse--shape discrimination methodshape discrimination method
3.3. Update on recent resultsUpdate on recent results
4.4. Summary/OutlookSummary/Outlook
2
Dušan BudjášDušan BudjášDušan Budjáš
3
BEGe publicationBEGe publicationMPIK HeidelbergMPIK HeidelbergMPIK HeidelbergDušan BudjášDušan BudjášDušan Budjáš
� submitted to JINST
� accepted for publication after some minor corrections
� ArXiv: 0909.4044 [nucl-ex]
� Contents:• charge collection
performance and stability
• PSD method and its calibration
• validation via coincident SCS and collimated 2.6 MeV beam
• experimental PSD results
� also: proceedings from CIPANP 2009 (4 pages, submitted to AIP)
� previously: IEEE 2008 proceedings arXiv: 0812.1735v1[nucl-ex]
0
0.2
0.4
0.6
0.8
1
0 0.2 0.4 0.6 0.8 1
distance from the read-out electrode, x [cm]
W
0
2
4
6
8
10
12
14
16
|Ew| [c
m-1
]
W(x)
|Ew(x)|
0
0.2
0.4
0.6
0.8
1
0.5 1 1.5 2 2.5 3 3.5 4
r [cm]
W
0
0.1
0.2
0.3
0.4
0.5
|Ew| [c
m-1
]
W(r)
|Ew(r)|
4
MPIK HeidelbergMPIK HeidelbergMPIK HeidelbergDušan BudjášDušan BudjášDušan Budjáš
BEGe pulse shape discrimination methodBEGe pulse shape discrimination method
BEGe (hypothetical)
True coaxial
( ) ( ) ( ) vtxEqvtxEqtI h
W
he
W
e ⋅⋅+⋅⋅−= )()(
ee−−
hh++
+HV
read-out
Ramo's theorem ⇒
ref: Knoll
0
0.2
0.4
0.6
0.8
1
0 0.2 0.4 0.6 0.8 1
distance from the read-out electrode, x [cm]
W
0
2
4
6
8
10
12
14
16
|Ew| [c
m-1
]
W(x)
|Ew(x)|
5
MPIK HeidelbergMPIK HeidelbergMPIK HeidelbergDušan BudjášDušan BudjášDušan Budjáš
BEGe pulse shape discrimination methodBEGe pulse shape discrimination method
BEGe (hypothetical)
( ) ( ) ( ) vtxEqvtxEqtI h
W
he
W
e ⋅⋅+⋅⋅−= )()(
-1000 -500 0 500 1000 1500 20000
200
400
600
800
Time after trigger [ns]
Am
plit
ud
e [a.u
.]
Interaction point distance from read-out electrode [mm]:
0
0.03
0.06
0.09
0.12
0.15
0.18
0 10 20 30 40 50 60 70 80 90 100
Time [ns]
Cu
rre
nt [a
. u
.]
0.4 1 2.5 4.5 6.5 8.2 9.7
ee−−
hh++
+HV
read-out
Ramo's theorem ⇒
simplified 1-dimensional calculation real recorded signal
0
0.2
0.4
0.6
0.8
1
0 0.2 0.4 0.6 0.8 1
distance from the read-out electrode, x [cm]
W
0
2
4
6
8
10
12
14
16
|Ew| [c
m-1
]
W(x)
|Ew(x)|
6
MPIK HeidelbergMPIK HeidelbergMPIK HeidelbergDušan BudjášDušan BudjášDušan Budjáš
BEGe pulse shape discrimination methodBEGe pulse shape discrimination method
BEGe (hypothetical)
( ) ( ) ( ) vtxEqvtxEqtI h
W
he
W
e ⋅⋅+⋅⋅−= )()(
-1000 -500 0 500 1000 1500 20000
200
400
600
800
Time after trigger [ns]
Am
plit
ud
e [a.u
.]
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0 10 20 30 40 50 60 70 80 90 100
Time [ns]
Cu
rre
nt [a
. u
.]
single site
multi site
energy normalised ~equal event energy
A A
ee−−
hh++
+HV
read-out
Ramo's theorem ⇒
simplified 1-dimensional calculation real recorded signal
MPIK HeidelbergMPIK HeidelbergMPIK HeidelbergDušan BudjášDušan BudjášDušan Budjáš
7
PSD parameter distributionPSD parameter distribution
DEP events accepted
rejected
SSE band
MSE regionFEP
1620.7 keV
FEP
2614.5 keVSEP
FEP
1620.7 keV
DEP
1592.5 keVSEP
2103.5 keV
FEP
2614.5 keV
1400 1500 1600 1700 1800 1900 2000 2100 2200 2300
0.33
0.333
0.336
0.339
Energy [keV]
m
fitted curve
1400 1500 1600 1700 1800 1900 2000 2100 2200 2300
-5
-2.5
0
2.5
5x 10
-4
Energy [keV]
fit re
sid
uals
<A
/E>
SS
E
8
MPIK HeidelbergMPIK HeidelbergMPIK HeidelbergDušan BudjášDušan BudjášDušan Budjáš
PSD calibrationPSD calibration
Compton 1425 ± 25 keV
Compton 2245 ± 25 keV
DEP ± 1 σ
exponential tail
Gaussian
fit function
A/E [a.u.]
Nu
mber
of
cou
nts
<A
/E>
SS
E
DEPMSE
SSE
228Th
1400 1500 1600 1700 1800 1900 2000 2100 2200 2300
0.33
0.333
0.336
0.339
Energy [keV]
m
fitted curve
1400 1500 1600 1700 1800 1900 2000 2100 2200 2300
-5
-2.5
0
2.5
5x 10
-4
Energy [keV]
fit re
sid
uals
<A
/E>
SS
E
9
MPIK HeidelbergMPIK HeidelbergMPIK HeidelbergDušan BudjášDušan BudjášDušan Budjáš
PSD calibrationPSD calibration
10
MPIK HeidelbergMPIK HeidelbergMPIK HeidelbergDušan BudjášDušan BudjášDušan Budjáš
PSD calibrationPSD calibration
Assuming gaussian distribution (resolution dominated by noise):2 σ ⇒ 97.7% SSE acceptancearbitrary choice of "SSE identification probability"
SSE defined as events with charge cluster extent so small that the electric field doesn't change significantly across it's width
2 σ
228Th
11
MPIK HeidelbergMPIK HeidelbergMPIK HeidelbergDušan BudjášDušan BudjášDušan Budjáš
Updated experimental results Updated experimental results
� cut at 2 σ from the SSE band mean
� simplified MC estimation of 0νββ acceptance: (89.4 ± 1.4)%
γ-lines
CC = Compton continuum (2039 ± 35 keV)
100%
10%
1%
0.1%
0νββ
12
MPIK HeidelbergMPIK HeidelbergMPIK HeidelbergDušan BudjášDušan BudjášDušan Budjáš
PSD validation via coincident singlePSD validation via coincident single--Compton scatteringCompton scattering
SCS
⇒ double-escape peak (DEP) is a good representation of ββ events
⇒ validated our PSD calibration using DEP and Compton continuum events
A/E parameter histograms:
no effect ofevent topologyor spatial distribution
corrected forenergy depen-dence from Compton cont.
SSE line
MSE region
102
101.5
101
100.5
accepted
rejected
SSE band near-electrode events
13
MPIK HeidelbergMPIK HeidelbergMPIK HeidelbergDušan BudjášDušan BudjášDušan Budjáš
PSD performance in dependence on spatial event distribution PSD performance in dependence on spatial event distribution
ee−−
hh++
Interaction point distance from read-out electrode [mm]:
0
0.03
0.06
0.09
0.12
0.15
0.18
0 10 20 30 40 50 60 70 80 90 100
Time [ns]
Cu
rre
nt [a
. u
.]
0.4 1 2.5 4.5 6.5 8.2 9.7
14
MPIK HeidelbergMPIK HeidelbergMPIK HeidelbergDušan BudjášDušan BudjášDušan Budjáš
acceptance: DEP 1621 keV
uncollimated: 89% 10%
collimated (centre): 88% 23%
DEP
amplified current amplitude A
reject accept
228Th source
ee−−
hh++
∅ 6 mm collimated beam
PSD performance in dependence on spatial event distribution PSD performance in dependence on spatial event distribution
0%
5%
10%
15%
20%
25%
30%
35%
0 5 10 15 20
Collimator distance from centre [mm]
Fra
ction o
f events
above S
SE
band
.
4000V 3s
4250V 3s
4500V 3s
3750V 3s
15
HV dependence of PSD performanceHV dependence of PSD performanceMPIK HeidelbergMPIK HeidelbergMPIK HeidelbergDušan BudjášDušan BudjášDušan Budjáš
< 3% of total volume PSD ineffectiveComplementary PSD techniques effectivealso in this region (e.g. rise-time based)
� the extent of the insensitive region grows with HV
ee−−
hh++
electrode extent
beam size
� PSD tested on ∅ 6 cm BEGe (at IRMM Geel, Belgium)
� results: SEP survival 9.2% (∅ 8 cm: 7.1%)FEP survival 13.5% (∅ 8 cm: 10.2%)at 89% DEP acceptance
8000
7000
6000
5000
4000
3000
2000
1000
01560 1580 1600 1620 1640
232-Th spectrum
after 2 σ PSD cut
γ 1588 keV DEP
γ 1621 keV
16
PSD performance in dependence on crystal sizePSD performance in dependence on crystal size
MPIK HeidelbergMPIK HeidelbergMPIK HeidelbergDušan BudjášDušan BudjášDušan Budjáš
1%
10%
100%
1500 1700 1900 2100 2300 2500 2700
Energy [keV]
surv
iva
l pro
bab
ility
228-Th with MPIK BEGe (8 cm); 3.8 kV
232-Th with IRMM BEGe (6 cm); 3.5 kV
232-Th with IRMM BEGe (6 cm); 3.1 kV
DEP
γ 1588 keV
γ 1621 keVγ 2615 keV
SEP
� PSD tested on ∅ 6 cm BEGe (at IRMM Geel, Belgium)
� results: SEP survival 9.2% (∅ 8 cm: 7.1%)FEP survival 13.5% (∅ 8 cm: 10.2%)at 89% DEP acceptance
17
PSD performance in dependence on crystal sizePSD performance in dependence on crystal size
MPIK HeidelbergMPIK HeidelbergMPIK HeidelbergDušan BudjášDušan BudjášDušan Budjáš
18
MPIK HeidelbergMPIK HeidelbergMPIK HeidelbergDušan BudjášDušan BudjášDušan Budjáš
� PSD validated with SSE events of different topology (DEP vs. SCS), spatial distribution, and energy
� discovered < 3% loss of MSE rejection sensitivity near the read-out electrode (specific to our PSD method)
� no spatial dependence of SSE acceptance found
� no change of PSD sensitivity in dependence on HV (except for a slight growth of the MSE-insensitive volume)
� PSD performance in smaller crystals likely different only due to lower γ-ray absorption efficiency
Summary and conclusionsSummary and conclusions
19
MPIK HeidelbergMPIK HeidelbergMPIK HeidelbergDušan BudjášDušan BudjášDušan Budjáš
� tests of FE electronics for bare BEGe operation in LAr
� optimisation of the PSD procedure and coordination with LNGS BEGe team in advance of acceptance testing of new BEGe's from depGe
� coordination with Zürich group (Francis) on definition of the Phase 2 calibration source from the point of view of PSD calibration requirements
OutlookOutlook
20
MPIK HeidelbergMPIK HeidelbergMPIK HeidelbergDušan BudjášDušan BudjášDušan Budjáš
Backup slidesBackup slides
FWHM
1.5
1.6
1.7
1.8
1.9
2
2.1
2.2
2.3
2.4
2.5
3500 3700 3900 4100 4300 4500
HV
keV
21
MPIK HeidelbergMPIK HeidelbergMPIK HeidelbergDušan BudjášDušan BudjášDušan Budjáš
HV scanHV scan
0
2
4
6
8
10
12
14
16
500 1000 1500 2000 2500 3000 3500 4000 4500
High voltage [V]
FW
HM
[keV
]
1.33 MeV (Co-60)
1.39 MeV (pulser)
0
5
10
15
20
25
30
35
40
45
50
2600 3100 3600 4100 4600
V
co
un
ts
0
1000
2000
3000
4000
5000
6000
7000
8000
ch
an
nel
peak intensity
peak position
22
MPIK HeidelbergMPIK HeidelbergMPIK HeidelbergDušan BudjášDušan BudjášDušan Budjáš
HV scanHV scan
0
2000
4000
6000
8000
10000
12000
500 1000 1500 2000 2500 3000 3500 4000 4500
High voltage [V]
Num
ber
of
counts
0
1000
2000
3000
4000
5000
6000
7000
8000
Peak p
ositio
n [
channel]
1.33 MeV peak intensity
1.33 MeV peak position
Nu
mbe
r o
f co
un
ts [
pe
r 60
0 s
]
23
MPIK HeidelbergMPIK HeidelbergMPIK HeidelbergDušan BudjášDušan BudjášDušan Budjáš
Charge collection characterisationCharge collection characterisation
59.4
59.42
59.44
59.46
59.48
59.5
59.52
59.54
-50 -40 -30 -20 -10 0 10 20 30 40 50
distance from center [mm]
pe
ak
po
sit
ion
[k
eV
]
0.4
0.5
0.6
0.7
0.8
0.9
1
FW
HM
[k
eV
]
peak position
FWHM
collimated 241
Am scan
59.3
59.35
59.4
59.45
59.5
59.55
59.6
0 5 10 15 20 25 30 35
distance from the top of crystal, d [mm]
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
FW
HM
[keV
]
peak position
FWHM
pe
ak p
ositio
n [ke
V]
gain variation: ≤ 0.055%
gain variation: ≤ 0.075%
� active mass: 836 g (95 % of total mass)
� dead layer:0.43 mm
59.5 keV
d
d
Energy [keV]
Co-60 (high rate)
Co-60 (high rate+pile-up reject)
Co-60 (low rate)
Num
ber
of
cou
nts
24
MPIK HeidelbergMPIK HeidelbergMPIK HeidelbergDušan BudjášDušan BudjášDušan Budjáš
Charge collection losses: peak tailsCharge collection losses: peak tails
25
MPIK HeidelbergMPIK HeidelbergMPIK HeidelbergDušan BudjášDušan BudjášDušan Budjáš
Charge collection stabilityCharge collection stability
-0.020%
-0.015%
-0.010%
-0.005%
0.000%
0.005%
0.010%
0.015%
22.12.08 29.12.08 5.1.09 12.1.09 19.1.09 26.1.09 2.2.09 9.2.09
Date
1333 keV
1174 keV
LN refilling
weekends
Re
lative p
eak p
ositio
n c
orr
ecte
d
for
puls
er
fluctu
ation
Setu
p
rearr
angem
ent
1st set 2nd set
Maximal variation: ≤ 0.015% ≈ 0.2 keV @ 1332.5 keV
26
MPIK HeidelbergMPIK HeidelbergMPIK HeidelbergDušan BudjášDušan BudjášDušan Budjáš
Charge collection stability: count rateCharge collection stability: count rate
2.60
2.75
2.90
3.05
3.20
0 7 14 21 28 35 42 49
Days since 22.12.2008
2.0
2.1
2.2
2.3
2.4
59.5 keV
1333 keV
Co
un
ts p
er
3 h
r
Co
un
ts p
er
3 h
r (c
orr
ecte
d)
×104
×104
27
MPIK HeidelbergMPIK HeidelbergMPIK HeidelbergDušan BudjášDušan BudjášDušan Budjáš
Coincident recordingCoincident recording
Struck SIS 3301
flash- ADC
14- bit, 100 MHz
pulse recording,
digital shaping
(τshaping = 10 µs)
1.6 µs
coincidence
window
software gate
Amplified raw signal
Canberra2002CSL
MPIKno shaping
TFACanberra2111
Time- filtered signal (10 ns differentiation and
10 ns integration time)
Amplified raw signal
Preamp
no shapingMPIK
228Th source(no collimator)
Pb/Cu shieldsolid
angle:~ 10°
25 c
m -
80 c
m
23.6 cm
28
HV dependence of PSD performanceHV dependence of PSD performanceMPIK HeidelbergMPIK HeidelbergMPIK HeidelbergDušan BudjášDušan BudjášDušan Budjáš
� current signal amplitude grows with HV => weighing field shape changes
� (the width of the SSE band seems to slightly increase with HV)
0.2
0.22
0.24
0.26
0.28
0.3
0.32
3500 3750 4000 4250 4500
V
<A
/E>
sse
0.005
0.0055
0.006
0.0065
0.007
sig
ma(A
/E_sse)