The PSI UCN source Status summer/autumn 2007: 1) Introduction 2) Source principle 3) R & D experiments UCN storage, losses and depolarization UCN production in solid deuterium 4) Some impressions
Feb 05, 2016
The PSI UCN source
Status summer/autumn 2007:1) Introduction2) Source principle3) R & D experiments UCN storage, losses and depolarization UCN production in solid deuterium
4) Some impressions
Zürich - Vancouver
Zürich - Vancouver
Switzerland
PSI
Paul-Scherrer-Institut
SLS:
600 MeV p cyclotron2 mA, 1.2 MW, since 1974Upgrade 2 MW (2009)
SR: ,SINQ: n
UCN: n
Proton cyclotron formedical application: p
PSI: 1200 employees1000 external users
Ring cyclotron: 600MeV, 2mA1.2MW (unique!)
Proton accelerator @ PSI
UCN Source
nEDM experiment
600 MeV
How do we make neutrons at PSI?
PSI UCN source
spallation target
1.2 MWp beam
2.5 m 2m3
Spallationsprozess
PSI UCN source
heavy water moderator
2.5 m 2m3
PSI UCN source
heavy water moderator
2.5 m 2m3
Lebensdauer in D2O: 5 msv = 2200 m/sReichweite: ~10 m
Spallation target: lead (82p + 126n)
Proton beam: 2mA (or more!) 1016 p/s
1 proton 10 neutrons 1017 n/s
~10 s Puls 1018 n/puls
Average neutron energy 2MeV 20’000 km/s
After ca. 30 bounces ~25 meV 2200 m/s
Neutron production at PSI (SINQ, UCN)
0.2 • 1013/cm2/mA0.40.81.02.04.06.08.010.0
Φ0 Thermal flux
sD2
Pb
Neutron flux at PSI UCN source
sD2 near target!
8 s-puls (1.2 MW):5 K 8 K
800 s no beam8 K 5 K
800s8s
Pulsed UCN source
800s8s
Pulsed UCN source
800s8s
Pulsed UCN source
UCN cold source
cold source
h = 2.5 mV = 2m3
v = 5 – 9 m/s
v = 0 – 7 m/s a
b
Coherent strong interaction surface potentialof solid deuterium (106 neV 4.5 m/s)
CuBe, DLC
Needs: storage volume coating ( storable neutrons ~vc3!)
50 100 150 200 250 300 35010-8
10-7
10-6
10-5
10-4
10-3
Lo
ss C
oe
ffic
ien
t
Fermi potential [neV]
low wall loss probability µ
long storage time
high Fermi potential
more UCN (v3) Al
Pb
Ni
C
Diamond
BeOBe 300 K
Be 70 K
58Ni
65Cu
Cu Fe
DLC
Storage materials
Detector count rate:
B
Sample
Magnet
UCN from ILL-turbine
Detector
B
105
1100 %
00 100 200 300 400 time [s]
wall material: loss and depolarization
2
4
6
8
DLC -VT300 K
Be -TUM300 KBe -
PNPIQuartz300 K
Be - PNPI380 K
Be - PNPI300 K
DLCPET 2300 K
DLCPET 270 K
DLCPET 1may
DLCAl-Foil300 K
DLCPET 1juneDLC
Al-Foil70 K
Wall loss coefficient [1 / wall collision]
x 10-4
DLC is a good choice also for (DLC)=1•10-6, (Be)=10•10-6
Diamondlike carbon
F. Atchison et al., Phys. Lett. B 625, 19 (2005).T. Brys et al., Nucl. Instr. and Meth. in Phys. Res. A 550, 637 (2005).
UCN transmission: Fermi potential
vc(Be) = (6.9 0.1) m/svc(DLC) = (6.9 0.1) m/s
F. Atchison et al., NIMB 260, 647 (2007),Phys. Lett. B 642, 24 (2006).
DLC:(6.9 ±0.2)m/s
F. Atchison et al.,NIMB 260, 647 (2007).PLB 642, 24 (2006).
Be:(6.8 ±0.2)m/s
UCN transmission: Fermi potential
Need to know for solid Deuterium:• UCN production cross section
– theoretical: Golub and Böning, ZPB51(1983)95
– experimental: F. Atchison et al., PRC 71, 054601 (2005).
• UCN lifetime – theoretical: Liu et al., PRB62(2000)R3581
– experimental: Morris et al., PRL89(2002)272501
• UCN mean free path– theoretical: incoherent cross section, inc = 4.1 barn
– experimental: F. Atchison et al., PRL 95, 182502 (2005).
solid D2: Motivation
~ 30ms
v = 5 m/s = 150 mm / 30 ms
h ~ 150mmR
mfp,
solid D2: Motivation
1000 – 100 m/s 100 – 10 m/s 10 – 0 m/s
cold very-cold ultra-cold
Transmission experiments UCN, VCN
Liquid Solid 12 hours
Preparation of sD2 (T = 18 K)
Thermal stress
Thermal stress IV Mean free path
1 cm
2 cm
8 cm
Cross sections
UCN
F. Atchison et al., PRL 95, 182502 (2005).
CN
sD2
UCN + CN
Detector
UCN
UCN production at SINQ, PSI
F.Atchison et al., PRC 71, 054601 (2005).
Empty cell
liquid D2 and gaseous D2 solidD2
UCN production at SINQ, PSI
F. Atchison et al., PRC 71, 054601 (2005).
Our experiment: F.Atchison et al., PRC 71, 054601 (2005).
Rsolid,8K = (1.11±0.23) x 10-8 cm-1
– in agreement with Z.-Ch. Yu et al., ZPB62(1986)137
Estimate for PSI UCN source:
CN ~ 2 x 1013 cm-2s-1mA
UCN ~ 30 ms
– 50% of equilibrium density after 4s proton pulse
UCN = Rsolid,8K x CN x UCN x 0.5 ≈ 5000 cm-3
2000 cm-3 in storage, 1000cm-3 in experiments
In Grenoble: ρ(UCN) = 10 UCN cm–3
UCN production at PSI
Ring cyclotron: 600MeV, 2mA1.2MW (unique!)
Where is the UCN source
UCN Source
nEDM experiment
Proton beam
Proton beam line
Proton beam
1000 A (10 ms)test beam September 6, 2007
UCN source
1.2 MW proton beam, UCN source, Exp. Areas
EDM > 1000 UCN/cm3
n
target
Test b
eam
1000
A, 10 m
s
S
eptem
ber 6,
2007
Experimental areas
test beam dump
Harp monitorsQuadrupole
collimator D2O circuit
Proton beam
Experimental floor
Existing
Proton beam line
Proton beam
PSI UCN source
spallation target1.2 MWp beam
2.5 m 2m3
Cold source
Relative Masses:Flat foil 100 %Torus 110 %Dome 131 %
50 cm
Torus
Dome
UCN tank fabrication
Vacuum box of UCN tank system
spallation target
target head iron shielding lead block target water pipes
D2 Gas System
He liquefier
D2 hut
D2 tanks
30 m3
Gas handling boxes
UCN-Tanksystem: Schwerwasser
8m3
D2O-Tanks
Pumpe(25 l/s)
Heat exchangers
Ion exchangers
Papers in 2003/04
1) Ortho-para equilibrium in a liquid D2 neutron moderator under irradiation PRB 68, 094114 (2003). 2) Spallation yields of neutrons produced in thick lead/bismuth targets by protons at incident energies of 420 and 590 MeV NIMB 217, 202 (2004).3) An apparatus for the investigation of solid D2 with respect to ultra-cold neutron sources NIMA 533, 491 (2004).
Papers in 2005
1) The simulation of ultracold neutron experiments using GEANT4 NIMA 552, 513 (2005).2) On the use of lead/tin alloys as target material for the production of spallation neutrons NIMA 539, 646 (2005)3) A fast kicker magnet for the PSI 600 MeV proton beam to the PSI ultracold neutron source NIMA 541, 598 (2005)4) Magnetron sputtered Be coatings as reflectors for ultracold neutrons NIMA 551, 429 (2005).5) Measured Total Cross Sections of Slow Neutrons Scattered by Gaseous and Liquid 2H2 PRL 94, 212502 (2005)6) Production of ultracold neutrons from a cold neutron beam on a 2H2 target PRC 71, 054601 (2005)7) Magnetic field stabilization for magnetically shielded volumes by external field coils NIMA 554, 527 (2005).8) A novel apparatus for the investigation of material properties for the storage of ultracold neutrons NIMA 550, 637 (2005)
Papers in 2005/06/071) First storage of ultracold neutrons using foils coated with diamond-like carbon Phys. Lett. B 625, 19 (2005). 2) Measured total cross sections of slow neutrons scattered by solid deuterium and implications for ultracold neutron sources Phys. Rev. Lett. 95, 182502 (2005).3) Storage of ultracold neutrons in a volume coated with diamondlike
carbon Phys. Rev. C 74, 055501 (2006).
4) Diamondlike carbon can replace beryllium in physics with ultracold neutrons Phys. Lett. B 642, 24 (2006).
5) The spallation target of the ultra-cold neutron source UCN at PSI NIMA 564, 51 (2006).6) A time-of-flight chopper for ultracold neutrons NIMA, 557, 572 (2006).7) Structural characterization of diamond-like carbon films for ultracold neutron applications Diamond & Related Materials, 16, 334 (2007).8) Measurement of the Fermi potential of diamondlike carbon and other
materials NIMB 260, 647 (2007).
On the way to the top!
Schedule: 1st UCN October 2008
PSI UCN source
heavy water moderator
2.5 m 2m3
Lifetime in D2O: 5 msv = 2200 m/sRange: ~10 m
PSI UCN source
heavy water moderator
2.5 m 2m3
Lebensdauer in D2O: 5 msv = 2200 m/sReichweite: ~10 m
spallation target
target head iron shielding lead block target water pipes
target construction
target construction
target head lead block water pipes
iron shielding block
target construction
Detector count rate:
B
Sample
Magnet
UCN from ILL-turbine
Detector
B
105
1100 %
00 100 200 300 400 time [s]
wall material: loss and depolarization
Detector count rate:
B
Sample
Magnet
UCN from ILL-turbine
Detector
B
105
1100 %
00 100 200 300 400 time [s]
wall material: loss and depolarization