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