Deuterium for ultracold neutron sources

1

Deuterium for ultra-cold neutron sources
Peter Fierlinger, PSI UCN Group
Collaboration Paul Scherrer Institut, Villigen,
Switzerland, Jagiellonian University, Cracow,
Poland,Institut Laue-Langevin, Grenoble, France,
Stefan Meyer Institut, Vienna, Austria,Kyoto
University, Kyoto, Japan, Osaka University,
Osaka, Japan, Joint Institute for Nuclear
Research, Dubna, Russia
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UCN source _at_ PSI
Tp 600MeV Ip 2mA 10n/p Per pulse 1017p
?1018n thermal flux 21014 s1 cm2 cold
flux 21013 s1 cm2 UCN 2105 s1 cm3 3103
cm3 stored
UCN storage volume 2m3
UCN shutter
solid D2 moderator
p beam

D2O moderator
spallation target
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Superthermal converter
Detailed balance
down-scattering
?
n
mod
UCN
mod

?
up-scattering
Solid Deuterium (sD2) Phonon excitation
Density of States
9.4 meV
Phonon Energy (meV)
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Source performance
mfp
density
rUCN FN R tUCN
(sinc rD2)-1 8 cm
mfp, t
t 30ms
R
h 150mm
v 5 m/s 150 mm / 30 ms
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UCN life time in (s)D2

• Nuclear absorption of neutrons on deuterons
• ?a 150 ms
• Phonon up-scattering (temperature dependent)
• ?up 40 ms for TSD2 8 K
• Para-D2 up-scattering (UCN -gt CN)
• ?p 150 ms for 1 para-D2

C. L. Morris et al., PRL 89, 202501 (2002)
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Transmission
camera
(s)D2
cryostat
neutrons
2D detector
chopper
Raman spectroscopy
cold very-cold
ultra-cold
1000 100 m/s
100 10 m/s
10 0 m/s
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Results
gas
liquid
solid
PRL94(2005)212502, PRL (2005, in press)
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UCN scattering
18K
5K, slowly cooled
5K, fast cooled
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Thermal stress
Light transmission through a sD2 crystal
Cross section
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UCN production _at_SINQ
Storage bottle
ID 65 mm,L 1080 mm
Ni mirror
Polarized beam !
CN flux 4.5107cm-2s-1mA-1
shutters
Proton beam current 1.2 mA
CN
Fe mirror
Detector
sD2
Magnetized B 2T
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Results
Rsolid,8K (1.110.23) x 10-8 cm-1
PRC71(2005)054601
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Conclusion Outlook
Source related

• Measured numbers confirm estimation for PSI UCN
  source
• Thermal stress does not influence the source
  performance
• Scattering cross sections for gas- liquid- and
  solid D2 were measured for a wide range of
  energies
• Ongoing
• Measurement of CD4, O2 as UCN converters
• (polarized) UCN production with polarized CN

Physics