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Measurement of Re-emission of Cherenkov Radiation. Yuri Kamyshkov / University of Tennessee Aqueous Scintillators Meeting at Temple University, January 19, 2010. Outline. Will talk about possible extension of Cherenkov radiation - PowerPoint PPT Presentation
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MEASUREMENT OF RE-EMISSIONOF CHERENKOV RADIATION
Yuri Kamyshkov / University of TennesseeAqueous Scintillators Meeting
at Temple University, January 19, 2010
Will talk about possible extension of Cherenkov radiation detection due to absorption and re-emission of Cherenkov light in wider wavelength range by the additives to water Will illustrate this mechanism with our work performed for organic scintillator in KamLAND that resulted in LS response non-linearity understanding measurement and correction
Will discuss our R&D plans for water studies
Outline
J.D. Jackson, Classical Electrodynamics3-rd edition, page 638
Cherenkov emission band
for LS 0 ~ 100 nm
PMT sensitivity
range
2 ; n
Cherenkov light emission
2222
2 1112
nβλπα
dxdNd mostly UV
Red UV
at threshold velocitiesCherenkov radiation starts with UV photons
Cherenkov yield in Super-K
Say, for relativistic muon with 2 in water:# of per cm produced between 300 and 600 nm [compare with 100 eV/ in typical LS ~10,000 / MeV ]
~ 347
# of photons per
dE dx MeV cmg
g g
@
0.25
MeV with 40% photocathode coverage say, 25m path for 100m attenuation len
~ 175~ 70~ 54.gth
~ 20% photocathode bac re5
k e-
~ 43.6~ 39.2
flection efficiency 90% averaged over typ incidence angle ~ 15.3% PMT average quantum efficiency
~ 6.0 p.e./ MeV
S-K reported ~ 6.0 p.e./ MeV
(simple estimate)
S. Fukuda et al., NIM A 501 (2003) 418–462
abso
rptio
n co
effici
ent
[cm
1]
inde
x of
refr
actio
n n
Refraction index and absorption coefficient for water from book of J.D. Jackson (3-rd edition)page 315
1 mm
1 m
PMT Q.E.
n
Wavelength, nm
Water data are from Segelstein, D., 1981: "The Complex Refractive Index of Water",M.S. Thesis, University of Missouri, Kansas City
Refraction index of water
(Yield 70-600 nm)/(Yield 300-600 nm) ~ 7.5
How Cherenkov photons with < 300 nm can be detectable?
Total energy of Cherenkov photons (for 70-600 nm)is ~ 20 times higher that 400 nm photons
Common “wisdom” for organic scintillators:
light yield is quenched for large dE/dx (Birks’ phenomenological law)
therefore quenching is important for p, , C-ions ...
but not for electrons ...
Non-linearity of e-m response is essential for detectors
related to the purpose of such precision LS neutrino experiments like KamLAND, Double Chooz, Borexino Daya Bay, NOA, HanoHano, SNO+, LENA ...
e.g. for antineutrino detection measured positron KE is almost equal to antineutrino energy which is used for determination of oscillation parameters
e p e n
Rela
tive
effici
ency
fo
r BC5
05 li
quid
sc
intil
lato
r
Calibration with monoenergetic radioactive sources in KamLAND
Strong non-linearity!
arbitrary normalization
Light yield in KamLAND ~ 270 spe/MeV with 1325 17”-PMTs (22% coverage) ~ 430 spe/MeV with + 554 20”-PMTs (34% coverage);
due to non-linearity L.Y. depends on the reference energy and might also depend on other factors (verified by periodic source calibration).
Two possible mechanisms that can produce non-linearity:(a) Birks’ quenching in scintillator(b) Cherenkov light production within of the PMT photocathode dxdEk
dxdELdxdL
B
10
GEANT recommendedBirks’ constant
Direct Cherenkovcontribution
Reasonablyexpected
Initial GEANT simulations in KamLANDwith two parameters reproducing non-linearity measured with
Region of solar in KamLAND
will dependon particularmechanism of non-linearity
Energy transferred by emission and re-absorption, and by molecular collisions—Forster mechanism.
Detectable PPO emission UV Cherenkov
incident
Dodecane80%
Pseudocumene20%
PPO~1.5 g/L
200 300 400 500 600 700
Wavelength, nm
0
0.2
0.4
0.6
0.8
1
Em
issi
on y
ield
(A.U
.)
Pseudocumene (PC) emissionQ.E. = 34% [Borexino]Excitation transfer to PPO via Forster mechanism is high, say ~65%
PPO emissionQ.E. = 80% [Borexino]
Conversion of UV to detectable light in LS
0 100 200 300 400 500 600 700
wavelength, nm
1
1.2
1.4
1.6
1.8
2
2.2
refra
ctiv
e in
dex
n
benzene (~ PC)
dodecane
__ Newton mixing__ Lorents-Lorenz mixing
Kosekimeasurement
Mixture of 80% dodecane + 20% benzene (neglect PPO)
n
Mixture of n-dodecane and pseudocumene
Mixing references: W. Heller, Physical Review vol. 68 (1945) 5-10;R. Mehra, Proc. Indian Acad. Sci. (Chem. Sci.), vol. 115 (2003)147-154
21
21
21 : Lorenz-Lorentz
fraction volumeis where, :Newton
22
22
221
21
12
2
222
211
2
nnv
nnv
nn
vnvnvn
mix
mix
imix
PMT
200 250 300 350 400 450 500 550 600 650 700
Wavelength, nm
10-5
10-4
10-3
10-2
10-1
100
101
102
103
104
105
Atte
nuat
ion
leng
th, c
mTransmission of KamLAND LS components
Mineral oil 80%
PPO ~1.5 g/L
PC 20%
100 m
D2 lamp
Electrometer for current measurements
Wavelength reading
Focusing elbow
UV LS re-emission flux calibration details
Si-photodiode (for flux calibration)
Vacuum tube to fore-pump
MgF2 window
Vacuum UV Monochromator
Vacuum tube for Si diode volume
Manual wavelength control
Turbo-molecular pump
Calibrated Si-diode (IRD/US Company) allows to measure photon beam intensity (# photons/sec) at every wavelength starting from 115 nm
No voltage bias is required(internal output impedance
of the diode ~ 100 M)
LS chamber with PMT
HamamatsuR329-02 PMT
LS/N2 OUT
LS/N2 IN
Direct protocathode coverage without reflections is ~ 0.6% of 4
MgF2 window
The goal is to measure the re-emission efficiency C() of UV photon (as produced by Cherenkov)to the “scintillation” photon emitted by PPO in LS
196.1 EGQECnII PMTPPOPMT
lightcollection
bkgrPMT
measPMT
Measured as (2.70.5)E+5
~ 22%
Measuredwith calibrated
Si-diode
Measured
Combined efficiency
Light collection efficiency can be studied by MC...But C() for PPO in LS is known for 300 nm as 80-100%
(80% is Borexino number)
100 150 200 250 300 350
Wavelength, nm
0.000
0.005
0.010
0.015
0.020
0.025
0.030
0.035
0.040
Com
bine
d ef
ficie
ncy
0
20
40
60
80
100 Re-em
ission probability %
Combined effin 150+300 nm rangeLiq. Scint, Liq. Scint
KamLAND LS re-emission probability normalized to Q.E. of PPO: 80% (Borexino)
0 100 200 300 400 500 600 700
wavelength, nm
0
1
2
3
4
5
n2 o
r eps
ilon
n2
Old single-resonance fit of Koseki measurements
222
22 112n
zdxd
Nd
Wavelengths where Cherenkov contributes
KamLAND LS refractive index (80% dodecane, 20% pseudocumene, 1.5 g/l PPO).
Reemission increases the number of Cherenkov photons detected at
1 MeV by factor of 3.7
0 100 200 300 400 500 600 700
Wavelength, nm
10-7
10-6
10-5
10-4
10-3
10-2
10-1
100
101
102
103
104
105
Abs
orpt
ion
leng
th, c
m
PSEUDOCUMENE 20%200-310 nm Extinction (with extr. tails)310-480 nm Borexino measurements480-700 nm Reyleigh scattering
MINERAL OIL 80%280-700 nm averaged measurementsof Hatakeyama
PPO 1.52 g/L200-330 nm Extinction 330-480 nm Borexino measurements480-700 nm Reyleigh scattering
Absorption lengths for LS components
Absorption of dodecane+PC mix
Total
PPOPCMOTot 1111
10 nm
Study of electron response with Compton spectrometer
Energy of recoil electron is determined by scattered photon
angle and certain initial energy of the incident photon
cos1
EmmEEE
e
ekine 22Na gamma source
0.511 MeV and 1.275 MeV
Compton spectrometer scheme
)(2211Nasource
1.6
m
Test sampleNaI
NaI
NaI
Scattering angle variation from 20 to 120 degrees.
Electron energies: 29-300keV and 166.3-1000keV
Compton Spectrometer
1 mCi 22Na source (511 and 1275 keV lines) inside massive lead collimator
LS test sampler=2.5cm radius,
h=6.35 cm quartz cylinder
NaI 13 cm1.6 m arm
NaI
VME DAQ system
Data & Monte-Carlo
Data
Monte-Carlo
70 degrees Data+Monte-Carlo
1.275MeV
0.511MeV
1.275MeV
0.511MeV
Backscattering in NaI
Backscattering in NaI
E, MeV(scintillator)
E, M
eV(N
aI)
ADC,
cha
nnel
s(N
aI)
ADC, channels(scintillator)
20 degrees Data 20 degrees MC
double ComptonScatteringdouble Compton
Scattering
Scintillator response to electrons
)(92.4168.0997.0 MeVEe parameterization
Systematic errors 0.5%
Oleg Perevozchikov, PhD thesis, UT 2009
GEANT simulations
Evis = Edep(E) m + NCh(E)
Calculated in GEANT, Birks dependent
Conversion of deposit energy into p. e.
Calculated in GEANT with reemission;
4.5% contributionat 1 MeV
(or ~ 20 s.p.e. / MeV)
Measured electron response is a ready product for electrons in GEANT: integrates Birks and Cherenkov non-linearity effects. For and positron simulation one needs n() and Birks’ coefficient.
Best fit (Monte-Carlo)N
umbe
r of p
hoto
ns/M
eV (s
cinti
llatio
n)
Birks,g/MeV/cm2
N p.e./MeV best fit is (609+110
–80) p.e.
in agreement withdirect yield measurement
N p.e./MeV=643.5+/-3.8 p.e.in Compton spectrometer
GEANT recommendedkB =0.013g/(MeV cm2) ∙
Fitted Birks value is kB=(0.01072 +0.0012
–0.0005) g/(MeV cm∙ 2)
=0.138mm/MeV
Comparison with and protons in KamLAND
proton quenching measurements
proton quenching MC
KamLAND data(gammas)UT MC(gammas)UT Data(electrons)UT MC(electrons)
LS response for and protons calculated without parameters compared with values measured in KamLAND
GEANT3 10 GeV muon in 6 cm liquid scintillator layer (normal incidence; KamLAND LS non-linearity)
How LS non-linearity would contribute in NOvA?
2 GeV electron in infinite size liquid scintillator volume(KamLAND LS properties)
15% effect dependent on LS properties(if neglected)
C()
con
vers
ion
effici
ency
LS re-emission efficiency (PMT readout)
Combined Efficiency of KamLAND LS ~ 20% PC
preliminary, no WLSF
~ 5% PC
New automatic UT vacuum monochromator
Our R&D Plans
Components solubility in water, stability, concentration, composition, removal of components, absorption competing with water, quantum efficiency, and emission timing should be considered.
For candidate components will measure and cross compare re-emission efficiency with our UV monochromator (integrated detector response vs Cherenkov ). Tune composition of components based on the measured efficiency vs . Spectral composition of re-emitted light could be very instructive for mechanism analysis (unfortunately, we are short of ~ $60K)
After finding the optimized composition, test light amplification effect with ~1 m3 cosmic muon water-Cherenkov detector that we have at UT. Hope that amplification factor of 5-10 can be achieved.
In collaboration with UT chemists (Shawn Campagna, Mark Dadmun) will identify photosensitive molecules with excitation range covering 70-300 nm; probably with 2-3 absorption and re-emission steps. With final emission in the visible (detector) range.