LEAD PERCHLORATE AS A NEUTRINO DETECTION MEDIUM
STEVEN ELLIOTT, PETER DOE, HAMISH ROBERTSON, TOM STEIGER, JOHN WILKERSON. UNIVERSITY OF WSHINGTON, SEATTLE
THE NUCLEAR PHYSICS OF LEAD
LEAD PERCHLORATE
ATTENUATION LENGTH OF 430 nm LIGHT
IN 80% Pb4(ClO4)2 (UNPURIFIED)
LEVEL SCHEMES
of the
208Pb  208Bi System
AS A
NEUTRINO DETECT ION MEDIUM
PROPERTIES OF A LEAD PERCHLORATE SOLUTIONS
CROSS SECTION COMPARISON
LEAD PERCHLOR AT E P b (C lO 4 ) 2 IS:
NEUTRON CAPTURE TIME IN 80 % Pb(ClO4)2
 HIG HLY SOLUBLE
500g m Pb ( ClO 4 ) 2 /1 0 0g m H 2 O
Den sit y = 2 .7 @ 80 % Con c.
LEAD I S AN EXCELLENT NEUT RIN O T ARGET :
 HIG H CROSS SECT ION
3n
 CC AND NC REACTIONS

  Pb Pb  

6.9
6.7
n capture (b)
Relative num.
den. w.r.t. Pb
n capture rate
w.r.t. H
204
0.70
0.01
0
206
0.03
0.24
0
207
0.70
0.22
0.04
208
Pb
0.02
0.52
0
35
Cl
44.00
1.52
18.3
0.43
0.48
0.06
0.00
13.57
0
17
0.23
0.01
0
18
O
0.00
0.03
0
H
0.32
11.3
1
Isotope
2n
IAS
Pb(n,e)x
Pb
Pb
58
43
0.66
0.23
4.5
1.4
91
59.6
Pb
37
Cl
16
O
O
'
e
NEU TRAL CU RRENT
x
12

208- Y
T=4 MeV
=3
T=8 MeV
=0
T=4 MeV
=3
T=8 MeV
=0
 DAR
Pb(,’)x
18
GT
Bi  X  Yn
208
Pb(e,e)x
2n

208
KL
Pb(,’)x
CHARG ED CU RRENT
e
208 Y
FHM
Pb(e,e)x
24 MeV
1st
  Pb Bi  e
208
 Spectrum
( Fu lle r e t al. Ast r o- p h / 9 80 9 16 4 )
 RELAT IVELY LOW COST
208
Transition
 units
10-40 cm2
1n
Pb  X  Yn
1n
6
FHM: Fuller, Haxton, McLaughlin, PR D59, 085005 (1999)
KL: Kolbe, Langanke, preprint Nucl-th\0003060
 CHA RGED P ARTI CLES
 CONTA INS CH LORIN E
Ne ut ron Ca pt u r e on Cl  8 .4 Me V ’s
35
Cl n ca pt u r e c r o ss se ct ion 44 .0 b
Pb
 GA MM A RAYS
$10 k / Tonne
(  100 t onne
@ 80 % con c. )
 APPEARS TRAN SP ARENT
No Obvious Features
Re fr ac t iv e Index = 1 .5 @ 80 % Con c.
May b e u se d a s a Ce r en k o v De t ec t o r
 Scattering or Absorption?
 WATE R BASED SOLUTION
Good ne ut ron m od e ra t o r
1 .7 x 10 21 208 Pb / cc ( 80% so ln .)
3 .6 x 10 22 H / cc
( 80% so ln .)
INDEX OF REFRACTION AS A FUNCTION
OF SOLUTION CONCENTRATION
DETE CTOR SH OU LD BE SENSITIVE TO:
0
 NEUTRO NS
SPECTRAL TRANSMISSION THROUGH A
1 CM CELL OF 80% Pb4(ClO4)2 (UNPURIFIED)
REFERENCED TO H2O
 RELATIVELY INEXPENSIVE
LEAD
CERENKOV
DETECTOR?
n capture time
~10-100 s.
DETE CTOR SH OU LD BE SENSITIVE TO:
Suspect limit due to Pb salt colloids possibly
due to reaction with dissolved gases
Need to understand chemistry better
measurements in progress
 Expect about 185 /cm
Stopping Power
0.2 cm/MeV (80%)
0.33 cm/MeV (50%)
15 MeV electron
~550  (80%)
~920  (50%)
 CHA RGED P ARTI CLES
Bi
 NEUTRONS
 GAMM A RAYS
APPLICATIONS
SUPERNOVA OBSERVATORY
 PHYSICS, OSCILLATIONS
Supernova Spectra
Cross Section
The cross section is strongly dependent on Te
6.27 MeV
Conclusions
1
Ratio for 2-n/1-n Events
NC events produce little energy in coincidence
with neutrons.
The CC-events will have electron energy in
coincidence with neutrons.
The CC electron energy can be sorted as to
how many neutrons were in coincidence.
In coinc., 2-n events are almost all due to e.
In coinc., 1-n events are due to e and anti- e.
This ratio is very
sensitive to Te.
Electron Neutrino Temperature (MeV)
2.1
Spectral Features
100
Energy (MeV)
8
1.7
1.3
Cross Section (10
100
Energy (MeV)
0
100
Measuring the electron energy
in coincidence with the neutrons permits
separation of NC and CC interactions.

0
1000
f
Measuring not just the total number of
neutrons but the number of events with
1 or 2 neutrons is very powerful.
0.1
0.1
cm /MeV)
10
2
-40
d/dE(10
1
100
-40
cm /MeV)
2
2
cm /MeV)
-40
d/dE(10
2.76 MeV
FHM indicates uncertainty of 50%.
KL and FHM differ by large amounts.
Decay at Rest (DAR)  from stopped p+ decay has spectrum similar to supernova, but with no anti-e.
A DAR  measurement in Pb(ClO4)2 studies the Pb reaction, without interference from the well known H reaction.
A 10 t detector could measure the cross section to 10% or so in a few months at proposed ORLaND facility.
f
10
f
100
Approximately thermal.
Absolute temperature scales are somewhat uncertain.
Relative temperature scales are not: there is a hierarchy, Te < Tanti-e < T,t.
Observation of Te > Tanti-e would be indicative of  oscillations.
1000
1000
Need to Measure 
10
1
0.1
0
6
0.9
0.5
0.5
4
0.1
0.1
2
Pb(ClO4)2 has the potential to make these
measurements because it is sensitive
to charged particles, gammas and neutrons.
Decay at Rest


p    
   e   e  
2
4
6
8
Electron Anti-Neutrino Temperature (MeV)
20 40 60
Energy (MeV)
Oscillations
Look for 29.8-MeV
e coming early in time.
tp = 26 ns
t = 2200 ns