Post on 13-Jan-2016
description
B.G. Cheon (Hanyang), H.J.Kim (KNU), E. Won
(KU), S.S. Myoung S.K. Kim(SNU), Y.J. Kwon (Yonsei)
We, Korean group reviewed possible options for the endcap ECL from the scratch.
The goal is to see if there are alternatives to pure CsI crystal option we have.
Parameters we looked at in particular : - light yield (energy resolution) - decay time (pileup, occupancy) - radiation hardness - beam background suppression - budget and other fabrication issues
Crystal CsI(Tl)
CsI BaF2 CeF3 BGO BSO PbWO4 LSO(Ce) GSO(Ce)
Density (g/cm3) 4.51 4.51 4.89 6.16 7.13 6.8 8.3 7.40 6.71
Melting Point (ºC) 621 621 1280 1460 1050 1030 1123 2050 1950
Radiation Length (cm)
1.85 1.85 2.06 1.65 1.12 1.15 0.9 1.14 1.37
Molière Radius (cm)
3.5 3.5 3.4 3.38 2.3 2.0 2.3 2.37
Interaction Len. (cm)
37.0 37.0 29.9 23.17
21.8 18 21 22
Refractive Index a 1.79 1.95 1.50 1.60 2.15 2.06 2.2 1.82 1.85
Hygroscopicity Slight Slight
No No No No No No No
Luminescence b (nm)(at peak)
550 320 300220
340300
480 480 420 420 440
Decay Time b (ns) 1300 356
6300.9
30 300 1002.4,26
3010
40 60
Light Yield b,c (%) 45 3-4 212.7
4-5 13 3-4 0.10.6
75 30
d(LY)/dT b (%/ ºC) 0.3 -0.6 -2~0
0.05 -1.6 -2.0 -1.9 -0.3 -0.1
Radiation hardness (rad)
103 104-5 106-7 106-7 105-6 106-7 106-7 108 108
Experiment CLEO BABAR Belle
BES III
KTeV,
E787
TAPS L3BELLE
CMSALICE
PANDA
-
a. at peak of emission; b. up/low row: slow/fast component; c. measured with bi-alkali PMT
Decay time ~30 ns which is 40 times faster than CsI(Tl). Solves pileup problem.
Light yield is ~5% CsI(Tl) and peak emission is 320 nm (UV region)
Radiation hardness may be OK (need to checked carefully) up to 1035
Readout by APD or P.P. No change to geometry of calorimeter Cost is ~$4/cc Currently under R&D by sBELLE group
Decay time with 40 ns. Solves pileup problem. Smaller radiation length and Moller radius
makes shorter and finer segmentation possible.
Radiation hard to 100MRad Light output is half of CsI(Tl), and peak
emission is 420 nm Use PD, APD or P.P. for photosensor LYSO has slightly more light output than LSO,
and may be easier to obtain commercially GSO has similar characteristics but has large
thermal neutron cross section LuAG:Pr is also good candidate except the cost Currently the cost is ~$30/cc!! Italian Endcap ECL default option
Decay time with 10& 30 ns. Solves pileup problem.
Smaller radiation length and Moller radius makes shorter and finer segmentation possible.
Radiation hard to 10MRad Light output is 0.1-0.6% CsI(Tl) Cooling to -25 degree with PMT shows
reasonable performance Peak emission is 420 nm Use APD or P.P. for photosensor CMS, PANDA is using Currently the cost is ~$3/cc
Optimization of the PbWO4 and increase of the light output
4x lighter if cooled down
0 200 400 600 800 10000
20
40
60
80
100
LY
/ p
.e./M
eV
integration gate / ns
-25oC
-10oC
-0oC+10oC+25oC
400 600 800 1000 1200 14000
1000
2000
3000
/E=18.2%
coun
ts
energy / a.u.
22Na
/E=11.5%
LY=92.2pe/MeV
400 600 800 1000 1200 14000
1000
2000
3000
/E=18.2%
coun
ts
energy / a.u.
22Na
/E=11.5%
LY=92.2pe/MeV
+80% at room T°
Development of the PWO-II : Light yield increased
Optimization of the PbWO4 (collaboration RINP, Minsk and the manufacturer BTCP at Bogoroditsk, Russia)
–reduction of defects (oxygen vacancies)–reduced concentration of La-, Y-Doping–better selection of raw material–optimization of production technology
incident energy / GeV
ener
gy r
esol
uti
on
incident energy / GeV
ener
gy r
esol
uti
on
3x3 matrix20x20x200mm3
PM-readout
Response to high energy photons @MAMI, Mainz
Calor2008
Main decay time is 100 ns. Smaller radiation length and Moller radius
makes shorter and finer segmentation possible.
Radiation hard to 1-10 MRad Light output is 3-4% of CsI(Tl), and peak
emission is 480 nm Use APD or P.P. for photosensor BSO:Ce shows stronger radiation hardness Beamtest results shows reasonable resolution Cost will be cheaper than BGO (No Ge) and
growing is easier (Cubic structure, low melting) Need to produced in large quantity (~$3/cc?)=> BSO option seems OK, if 100 ns decay time is
OK
Pure CsI is baseline option, however it may be problem with higher luminesity (>1035)
L(Y)SO, PbWO4 and BSO are reasonable option. BSO seems the most reasonable next candidate
considering all characteristics if it can be produced large quantity. If we can cool down to -25 degree, PWO is the best candidate since it is being produced large quantity.
BSO and PWO costs ~3$/cc & can be used with 20cm length with finer segmentation.
Detail study and comparison of different candidates coupled with photo sensor are necessary to select the best performance one.
APD orPP
Pure CsI Used CsI(Tl)
Endcap ECL upgrade : 11 M USD (8.2M for crystals)Crystal costs ¼ of full crystal 2 M total <5 M should be OK
Logic (and probably advantages)
1.Radiation damage only to front ~10 cm of crystals need to be checked2.High energy signals enough signal in CsI(Tl) crystals ->do not lose resolution3.Fast/Slow another handle for shower correction by knowing shower shape4.Fast trigger signal using fast signal blind to beam background5.Much cheaper
An alternative idea
SNU
FastSlow
A phoswich ('phosphor sandwich') is a combination of scintillators with dissimilar pulse shape characteristics optically coupled to each other and to a common PMT. Pulse shape analysis distinguishes the signals from the two scintillators, identifying in which scintillator the event occurred.
Etot = E1*a + E2*ba,b : calibration factor1) E2=0 : 1st crystal
interaction2) E1=0 : 2nd crystal
interaction3) Both : Etot can be
calculated
Idea: re-use (possibly) un-damaged rear part of endcap CsI(Tl) crystals
CsI(Tl)Pure CsI
SNU
CsI 8cm*8cm*30cm
-15cm +15cm
Gamma: 100 MeV 200 MeV 400 MeV 500 MeV 1 GeV
10cmPure CsICsI(Tl)
Note the difference in the emission spectrum of two X-tals
E_dep_pure
->N_photon according to Intensity
->Apply transmission curveSome transmit to csi(Tl)->fast signalOther + E_dep_Tl slow signal
SNU
E10/Etot
E5/Etot
E10/EtotE10/Etot
E10/Etot>0.5 >0.7
10MeV: 83% 82%100MeV: 86% 73%1GeV: 51% 13%
One Crystal
SNU
100 MeV
200 MeV
500 MeV 1 GeV
E(pure) vs. E(CsI(Tl))
E=a*E(Tl )+ b*E(pure)fit to each energy distribution
σ /E
E
5 cm
Energy resolution is 2% at 1 GeV
SNU
30cm*30cm*30cm
Two Belle type of crystals were received from KEK and cut into test samples (1x1x1cm3) for this study. They are polished and wrapped with Teflon sheet.
Maxium 40 keV x-ray energy is used for luminescence test
2” bi-alkali high gain PMT is used for 662 keV gamma and 5.5 MeV alpha-ray test.
Configuration 1. 1x1x1cm3 cubic CsI2. 1x1x1cm3 cubic CsI:Tl3. 1x1x2cm3 CsI+CsI:Tl (from 1 &2)
Small size Crystal R&D
KNU
X-ray
X-rayX-ray
X-rayemission
emission
emission
emission
Pulse heightDecay time
Pulse heightDecay time
Pulse heightDecay time
Q: Does emission of CsI de-excite CsI:Tl ?
Pure CsI
CsI(Tl)
KNU
Am241, Cs137
KNU
310 nm490 nm ??
Pure CsI CsI(Tl)
550 nm
Pure to Tl
490 nm
Tl to pure
550 nm
Strange enhancement !!!
Because of the mystery above, we cannot draw any conclusions
KNU
Am-241(alpha)
Cs137(gamma)
Am-241(alpha)
Am-241(alpha)
Pure to TlPure CsI
KNU
Test setup for cosmic rays
T.Y.Kim HYU Physics
Hybrid signal shape measurement @ sbelle Korea Meeting Page 20
CsI
(Tl)
Power Supply(HV)
-1500V
Amplifier FADC 400MHz
Linux PC
PMT
(High gain
Xp2206) 20cm
CsI
(pure)10cm
ULS Notice Korea
Fedora core 6
HYU
Cosmic ray - Data
T.Y.Kim HYU Physics
Hybrid signal shape measurement @ sbelle Korea Meeting Page 21
CsI (pure)
CsI
(Tl)
CsI
(pure)
HYU
Cosmic ray - Data
T.Y.Kim HYU Physics
Hybrid signal shape measurement @ sbelle Korea Meeting Page 22
CsI (Tl)
CsI
(Tl)
CsI
(pure)
HYU
Phoswich option may reduce the budget significantly (5 cm pure CsI costs < 5M US $).
Geant4 simulation (very preliminary) shows the energy resolution is ~ 2% at 1 GeV.
E = a*E(pure) + b*E(CsI(Tl)) seems to make everything complicated.
Phoswich x-ray luminescence shows a strange behavior (need to understand, calibration issue?).
Phoswich fast and slow components are 50:50 % in the signal.
More R&D is needed to understand situation better.
Pure CsI is a default option We are looking at - LSO : expensive but others look fine- BSO : decay time 100ns, no mass production- PbWO4 : operation at -25 oC is desired
as feasible alternative options Phoswich[CsI:CsI(Tl)] has been studied. We would like to continue R&D efforts to reduce
number of options, if not one option