Energy resolution of several scintillating crystals using different readout systems.

Energy resolution of several scintillating crystals
using differents readout systems
Measurements performed during Jul-Sept 2007 at the GSI
Mart´ın Gasc´on
Particle Physics Departament
University of Santiago de Compostela
5th. October, 2007
Mart´ın Gasc´on Energy Resolution of several scintillating crystals 5th. October, 2007 1

Contents
Tests performed
1 Energy resolution calibration using 1 cm3 CsI(Tl)
2 Energy resolution of CsI(Na) and BGO using APDs
3 Comparison between APDs and PIN Diodes
4 Energy resolution of LaBr3 using PMTs
5 Energy resolution of LaCl3 using PMTs
6 Non-Uniformities measurements
7 Best values obtained for energy resolution

1. Energy resolution calibration
using 1 cm3
CsI(Tl)

Energy resolution calibration using 1 cubic cm CsI(Tl) + APD
Experimental setup
The detector is electrically isolated by a grounded Faraday box
The detector and Preampliﬁer are placed in a metalic box with a humidity control system
The system is temperature monitorized

Bias Voltage Optimization
Bias Voltage Photopeak ch. Energy Resol. Photopeak ch. Energy Resol.
300 937.3 ± 0.3 4.87 ± 0.08 937.1 ± 0.4 4.90 ± 0.08
320 1254 ± 0.5 5.12 ± 0.09 1258 ± 0.5 5.16 ± 0.10
340 1698 ± 0.7 5.37 ± 0.10 1705 ± 0.6 4.83 ± 0.09
360 2357 ± 0.9 5.23 ± 0.09 2366 ± 0.9 4.79 ± 0.09
380 3255 ± 1.3 5.14 ± 0.09 3266 ± 1.2 4.75 ± 0.08
400 4517 ± 1.8 4.97 ± 0.08 4527 ± 1.6 4.57 ± 0.08
420 6211 ± 2.3 4.62 ± 0.08 6222 ± 2.2 4.54 ± 0.08
430 7275 ± 2.7 4.74 ± 0.09 7285 ± 2.7 4.71 ± 0.08
Table: Photopeak position vs Bias Voltage
Spectra for each Bias Voltage are taken twice,
in order to check stability and to reduce
uncertainties

Not saturated between 300 V and 420 V
There is no minimum in the energy resolution

Bias Voltage Amp. gain Photopeak ch. Energy Resol. Photopeak ch. Energy Resol.
360 135 6307 ± 2.3 4.51 ± 0.08 6304 ± 2.3 4.81 ± 0.09
370 113 6330 ± 2.3 4.71 ± 0.08 6332 ± 2.3 4.59 ± 0.08
380 96 6330 ± 2.2 4.61 ± 0.08 6326 ± 2.4 4.62 ± 0.08
390 81 6335 ± 2.4 4.85 ± 0.09 6340 ± 2.3 4.74 ± 0.08
400 69 6296 ± 2.4 4.92 ± 0.09 6302 ± 2.3 4.74 ± 0.09
410 59 6333 ± 2.3 4.71 ± 0.09 6333 ± 2.3 4.83 ± 0.09
Table: Photopeak position vs Bias Voltage
Varying Bias Voltage and Ampliﬁer gain to keep
constant the photopeak channel
There is minimum of energy resolution around
380 V

Ampliﬁer Gain
Linear along the whole dynamic range
the higher the Ampliﬁer gain, the better the energy resolution

Acquisition Time
There is a statistical deﬁcit below 40 seconds
60 seconds give us a good energy resolution

Shaping Time
3 µs and 6 µs are a good trade-off

Final energy resolution
Temp. o
C Photopeak ch. Energy Resol. Photopeak ch. Energy Resol.
24.3 ± 0.1 6156 ± 2.3 4.96 ± 0.09 6154 ± 2.4 4.87 ± 0.09
24.3 ± 0.1 6159 ± 2.4 5.08 ± 0.09 6156 ± 2.4 5.04 ± 0.09
24.3 ± 0.1 6159 ± 2.3 4.75 ± 0.09 6152 ± 2.3 4.65 ± 0.09
24.3 ± 0.1 6157 ± 2.5 4.97 ± 0.09 6155 ± 2.4 4.93 ± 0.09
24.3 ± 0.1 6151 ± 2.3 4.81 ± 0.09 6155 ± 2.4 4.86 ± 0.09
Table: Ten spectra acquired for st = 3µs, t = 50s, HV = 380V and G = 105
Temp. o
C Photopeak ch. Energy Resol. Photopeak ch. Energy Resol.
24.3 ± 0.1 6220 ± 2.2 4.59 ± 0.08 6221 ± 2.3 4.68 ± 0.08
24.3 ± 0.1 6219 ± 2.3 4.74 ± 0.09 6219 ± 2.2 4.68 ± 0.08
24.3 ± 0.1 6219 ± 2.2 4.60 ± 0.08 6222 ± 2.2 4.59 ± 0.08
24.3 ± 0.1 6220 ± 2.3 4.65 ± 0.08 6221 ± 2.2 4.63 ± 0.08
24.3 ± 0.1 6216 ± 2.2 4.55 ± 0.08 6219 ± 2.3 4.73 ± 0.09
Table: Ten spectra acquired for st = 6µs, t = 50s, HV = 380V and G = 96
3 µs: Mean value: 4.89 ± 0.09 - Best value: 4.65 ± 0.09
6 µs: Mean value: 4.64 ± 0.09 - Best value: 4.55 ± 0.08

Energy resolution vs Energy
1170 keV is part of Comptom edge of 1332 keV of 60Co
The energy resolution is function of the square root of the incident energy photon
We used a 60Co, 137Cs and 152Eu sources

Energy resolution
The reported energy resolution obtained is 4.55 % is similar to the obtained in
”Optimization of energy resolution obtained with CsI(Tl) crystals for the R3B
Calorimeter” M. Gasc´on et al., Submited to IEEE Transactions on Nuclear
Science.

Albert Einstein
A theory is
something nobody
believes, except the
person who made it.
An experiment is
something everybody
believes, except the
person who made it.

2. Energy resolution of
CsI(Na) and BGO using APDs

Energy resolution of CsI(Na) and BGO using APDs
Experimental setup
Frustum shape crystals (170 mm length)
All are encapsulated into aluminium shielding
9x9 and 15x15 windows (1mm thick) (Face A and B)
Delivered by Scionix Holland.

Experimental setup
The detector is electrically isolated by a grounded Faraday box
The detector and Preampliﬁer are placed in a metalic box with a humidity control system
The system is temperature monitorized

CsI(Na) - Shaping Time - Face A
between 1 and 3 µs the energy resolution is approximately constant
3 µs requires the lowest ampliﬁer gain

CsI(Na) - Acquisition Time - Face A
80 seconds is a good trade-off

CsI(Na) - Ampliﬁer Gain - Face A
Linear along the whole ampliﬁer dynamic range
500 is the situable one

CsI(Na) - Ampliﬁer Gain - Face A and B
Face B provides more light collection
The higher the light collection, the better the energy resolution
300 is selected for Face B

CsI(Na) - Acquisition Time - Face A and B
The higher the light collection, the better the energy resolution

BGO - Shaping Time - Face B
between 1 and 2 µs the energy resolution is approximately constant
1 µs requires lower ampliﬁer gain

BGO - Ampliﬁer Gain - Face B
500 is selected, above this value noise is ampliﬁed.

BGO - Acquisition Time - Face B

African Proverb
Not to know
is bad. Not to
wish to know is
worse.

3. Comparison between
APDs and PIN Diodes

Comparison between APDs and PIN Diodes
Experimental setup
Filter + Preamp made by GSI
No chance of varying Bias Voltage

Ampliﬁer Gain
Bad energy resolution
PINs Don’t need High Voltage
Faster stabilization

Acquisition Time
similar behavior to Hamamatsu
70 seconds is appropriated

Shaping Time
1 µs and 6 µs are minima

Experimental setup
Canberra 2001A Preampliﬁer
PIN Diode S3590-08 from Hamamatsu

Bias Voltage
PINs require much lower Bias Voltage
Faster stabilization (stable between 40 V and 80 V)

Bias Voltage
60 V is selected
Energy resolution is 2 % worse for PIN diode

Ampliﬁer Gain
750 is selected

Acquisition Time
Similar behavior to Hamamatsu
60 seconds is adecuated

Shaping Time
3 µs and 6 µs are good trade off for both
Pin Diode are too noisy, so that they can not resolve energies below 400 keV
Pin Diode has worse energy resolution, but similar trend for energies above 500
keV

4. Energy resolution of LaBr3
using PMTs

Energy resolution of LaBr3 using PMTs
R329 - Experimental setup
Brillance 380 (Saint Gobain)
R329 Hamamatsu PMT

R329 - Bias Voltage
Last point is out of the curve

R329 - Bias Voltage
Varying Bias Voltage and Ampliﬁer gain to keep constant the photopeak channel
1050 V is selected

R329 - Ampliﬁer Gain
Not linear for gain higher than 40
36 is selected

R329 - Acquisition Time
120 seconds is selected

R329 - Shaping Time
1 µs and 2 µs are good trade off
after 2 µs saturates

XP1918 - Experimental setup
Brillance 380 (Saint Gobain)
XP1918 Photonis

XP1918 - Bias Voltage
After 1100 V is saturated

XP1918 - Ampliﬁer Gain
Not linear from 40
36 is adecuated

XP1918 - Acquisition Time

XP1918 - Shaping Time
1 or 2 µs are selected

XP1918 - Energy resolution
4.11 % is the lowest energy resolution without saturation.

XP1918 - Energy resolution
The presented by Saint Gobain resolutions could be saturated
The relation between Photopeak channel/Compton is higher

5. Energy resolution of LaCl3
using PMTs

Energy resolution of LaCl3 using PMTs
Experimental setup
R329 PMT from Hamamatsu
Brillance 350 - 10 cm LaCl3 (1 and 2 windows)

R329 - Bias Voltage
After 1200 V is saturated

R329 - Bias Voltage
Varying the gain and Bias Voltage
1050 V is adecuated

linear
40 is selected

R329 - Acquisition Time

R329 - Shaping Time
1 or 2 µs are selected

Covering the window with aluminized mylar
linear
60 is selected

R329 -Energy resolution
5.78 % is the best energy resolution achieved.

6. Non-Uniformities measurements

Non-Uniformities measurements
Experimental setup
To collimate the source, we use Lead blocks of 5 cm length

Non-Uniformity definitions
Non Uniformity in the Ligth Output
is one of the factors worsening the energy resolution
at least, 2 methods are used to define it: G and δ
Definition of G
G =
LOmax − LOmin
LOmed
(1)
Definition of δ
LO
LOmed
= 1 + δ(
x − xmed
xmed
) (2)
Notes
δ-value is independent of the number of measuring points, but G does not
infinite number of measuring points means G = 2 · δ
Example:
For a 10 cm lenght crystal, if we measure 9 points every 1 cm, we get:
G = 1.6 · δ
(1) D.M. Beylin, et al., Nucl. Inst. and Meth., vol. A541, pp 501-515, 2005.
(2) G. Ren, X et al.,Nucl. Inst. and Meth., vol. A564, pp 364-369, 2006.

10 cm CsI(Tl) + APD + PMT
Spectra were taken using Cs-137 and Co-60 sources
Fitting the photopeak channel from the 1332 MeV gamma of a Co-60 source

G = 16.7 %; δ = 9.28% for 10 cm CsI(Tl) + HAMA
G = 9.6 %; δ = 5.33% for 10 cm CsI(Tl) + XP1918

Increasing the PMT gain and plotting as a function of distance to APD
Using a 1332 keV of Cobaltum 60 source (5 min/point)

Doing the sum of the photopeak channel for both

CsI(Na) - Non Uniformity in light collection - Face B
Collimated source of 60Co by 5 cm of Lead
Face A produced few light to perform this test

7. Best values obtained
for energy resolution

Best values obtained for energy resolution
Energy resolution
Crystal lenght Readout Prempliﬁera
Shaping Bias Volt. Energy Resolutionb
CsI(Tl) 1 cm APDc
Canb. 2001 6 µs e-m 4.50%
CsI(Tl) 1 cm Pin GSI-Preamp 6 µs - 18.7%
CsI(Tl) 1 cm Pin Canb. 2001 6 µs e-m 6.45%
CsI(Tl) 10 cm APD Canb. 2001 6 µs e-m 5.36%
LaBr3 3 cm R329 - 2 µs Wenzel 4.54%
LaBr3 3 cm XP1918 - 2 µs Wenzel 4.11%
CsI(Na) 17 cm APD Canb. 2001 3 µs e-m 17.1%
BGO 17 cm APD Canb. 2001 1 µs e-m 23.7%
LaCl3 10 cm R329 - 1 µs Wenzel 5.70%
LaCl3 (2w) 10 cm R329 - 1 µs Wenzel 8.35%
a
The Ampliﬁer used was Ortec 572
b
Energy Resolution for the 662 keV photon of a Cs-137 source
c
APD is S8664-1010 from Hamamatsu

Conclusions
The calibration showed that the energy resolution value of 4.5 % is repeated with different electronic
chains
The enery resolution of CsI(Na) and BGO are bad because its bad quality
The used window for the frustum like crystals produced an energy resolution worsening
There is difference of aproximately 4 % in the energy resolution between Face A and B in frustum like
crystals
The Filter and Preampliﬁer made by GSI for Pin Diodes don’t offer an energy resolution comparable to
Canberra Preampliﬁer
Pin Diodes don’t need High Voltage, are stable between 40 and 80 V, have an energy resolution of 6.5
% for 662 keV photons
Pin Diodes has worse energy resolution for low shaping times and for incident energies below 400 keV
than APDs.
LaBr3 produces so many light in a so short time that saturates common PMT working at tipical voltage
values
Working at linear gain, the best energy resolution obtained for LaBr3 was 4.11 % for XP1918 PMT from
Photonis
The best energy resolution for LaCl3 was 5.78 % for the R329 PMT from Hamamatsu

Bibliography
Technical Proposal for the Design, Construction, Commissioning and Operation of R3B.
http://www-land.gsi.de/r3b/
H. Alvarez−Pol et al. A ﬁrst proposal for the geometry of the Total Absorption Calorimeter
design at R3B. Internal Note: R3B CAL 01/05. http://www.usc.es/genp/
C.W.E. van Eijk, P. Dorenbos, E.V.D. van Loef, K. Kramer, H. Gudel ”Energy resolution of
some new inorganic-scintillator in gamma-ray detectors” Radiation Measurements, vol. 33, pp
521-525, 2001.
Hamamatsu Photonics: Photomultiplier Tubes and Related Products
D.M. Beylin, A.I. Korchagin, A.S. Kuzmin, L.M. Kurdadze, S.B. Oreshkin, S.E. Petrov, B.A.
Shwartz, ”Study of the radiation hardness of CsI(Tl) scintillation crystals,”
Nucl. Inst. and Meth., vol. A541, pp 501-515, 2005.
G. Ren, X. Chen, S. Lu, Z.Li, X. Xue, D. Shen, ”Non-uniformity of light output in large-sized
CsI(Tl) crystals grown by non-vacuum Bridgman method”,
Nucl. Inst. and Meth., vol. A564, pp 364-369, 2006.

Albert Einstein
Put your hand on a hot stove
for a minute,
and it seems like an hour.
Sit with a pretty girl
for an hour,
and it seems like a minute.
That’s relativity.

Energy resolution of several scintillating crystals using different readout systems.

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