He-II spallation UCN sourceand

possibility at TRIUMF

Y. Masuda (KEK)TRIUMF, Sep. 13, 2007

Experiments with high density UCNn EDM, ! decay, gravity, neutron reaction

Spole

Npole

! !"#$$"Å

%&'()*+,"-./,)01$"()2345

6/&7+*89$$"()23:

;*.:<"+(":&*)/+&=

>*/.('"??#"()2"0#@A+5

NS

)

BC)&D

"

E=*/&,.=F"()G*/.(

He-II in spallation n source

Spallation nproduction

n/p

Proton energy, Ep (MeV)

400

MeV

1 GeV

4.4 n/p

17.8 n/p

K. Tesch (1985)

n/p

200

MeV

1.3 n/p

6.7 n/p

500

MeV

Neutron productionnormalized by power

!"# $"#% &"$

!"' %"% '"'

!"% (") (")

& *"+ &)"*

$ &!"( ('

!

#

'

(

*

&!

&#

! !"% & &"% # #"% $

,-./.01202-34156278

92:/-.0;,-./.0

Neutron source parameters

!

dwelling time, heating

Ep

SpallationTarget

"s

"a

! heating

absorptionlifetime

Moderationheating

Mean freepath "neutron

m: mass

proton

nucleusM: mass

Lethargy# = -ave(ln(Ef/Ei))

= 2/(M/m +2/3)

" = 1/(N$s)

N: density

$s : scattering

%a = 1/ (N$av)

$a : absorption

moderation, diffusion,

Moderator material

! ! ! ! ! ! ! ! H2O!! D2O!! D2! ! Be! ! C!! ! Pb

Lethargy! ! ! ! 0.95!! 0.57!! 0.75!! 0.21!! 0.16!! 0.01

Mean free path!! 0.29!! 2.2! ! 6.0! ! 1.2! ! 2.6! ! 2.7(cm)! " = 1/(N$s)

Density N (1023/cm3) 0.34 0.33 0.25 1.24 0.80 0.33

Scattering $s (b) 103 13.6 6.8 7.0 4.8 11.3

Life time (ms)! ! 0.21!! 100!! 177!! 3.46!! 13!! ! 0.81 %a = 1/ (N$av)

Absorption $a (mb) 665 1.23 1.04 7.6 3.53 171

High #n(1 meV): high lethargy and short mean free path, low absorption ( = low ! heating)

UCN productionin He-II

Coherent inelastic neutron scattering in He-II

Born approximationd2$/dQd&

= kf/ki a2 S(Q,&)

a: coherent scattering length

Golub and Pendlebury

S(Q,&)

in

He-II

phononneutron

M.R. Gibbs et al. (1999)

ki

kf

UCN density in

' = {" $coh(Ein(E) dE} NHe )n %s0

Ec

)n : cold neutron flux ∝ proton beam power

%s : storage timedepends on 3He impurity and He-II temperature

Ec: maximum UCN energy ∝ Ec

3/2 : volume of momentum space

He-II advantagesHe-II SD2

cross section $coh = 0.76 b $coh = 2.48 b

dispersion curve single overlap better overlap

%a = 1/('v$a) # 0.2 s

structure almost vacuumdislocation, defect

ortho/para

mean free path >> 1 m several cm

Fermi potentialnegligibly smallno acceleration

109 neVacceleration

temperature < 2 K 5 or 6 K

heat conduction excellent not so good

Loss

Extraction

Thermalconductivity

UCNproduction

He-II can be placedin a spallation neutron source

Cold neutron flux *n in a spallation source higher than cold neutron guide

1012/s.cm2 possible in the spallation source

Liq.He

11KD2O

He-II

3Hecryostat

4Hecryostat

To 4Hepump

55 KSRD220110 K215 K

To 3Hepump

UCNguide

Isopure 4He

circulator

3He

circulator

UCN

detector

Spallation target

300KD2O

Graphite

Heater

1.25m

3 m

Shield of

1 m iron

0.5 m concrete

UCN

valve

Turbo

triscrol

dry

pump

Liq. He

Dry pump

Tank

Thermal

sink

0.7K

0.8K

0.9KPrototype UCN source (KEK)

He-II in spallation source

Radiation shield

3He pump

4He pumpUCN guide

He-II cryostat

p beam

UCN

detector

Liquid He

Proton beamline

(RCNP, Osaka)

400 MeV cyclotron

UCNsource

UCN pro

ton b

eam

line

16 m

2.5m

30

m

3 m

Ou

tsid

e

Liq.He

19KD2O

He-II

3Hecryostat

SRD220

To 3Hepump

UCN guide

UCN

detector

Spallation target

300KD2O

Graphite

Heater

1.25m

3 m

Shield of

1 m iron

0.5 m concrete

UCN

valve

UCN productionwith a proton pulse

of 1 s p

n

phonon

UCN

open

Data !"#$%&'()*+$,'-.*$/*012)$34*%)+'5

6

7666

86666

87666

96666

97666

6 96 :6 ;6 <6 866

,'-.*$/*012

"&'().

full energyabsorption

loss of charge collection

and noise

n + 3He ! p + t + 0.77 MeV

1

10

100

1000

10000

100000

0 50 100 150 200

Time (0.5 s/ch)

Cou

nts

/Tim

e b

in/C

ycl

e

Discri. Low

Discri. High

1micro A proton

" = 5.9 sFull absorption at the guide end

Diffusion from He-II to detector

UCN production with a proton pulse of 1s

Prompt background

Liq.He

19KD2O

He-II

3Hecryostat

SRD220

To 3Hepump

UCN guide

UCN

detector

Spallation target

300KD2O

Graphite

Heater

1.25m

3 m

Shield of

1 m iron

0.5 m concrete

UCN

valve

Decrease the aperture

p

n

phonon

UCN

open

annular disk1-cm diam

0.1

1

10

100

1000

10000

100000

0 50 100 150 200

Time (0.5s/ch)

Cou

nts

/ T

ime

bin

/ C

ycl

e 0.9K

1.0K

1.1K

1.2K

1.4K

Proton

With the annular disk

Going back and forth betweenthe disk and He-II bottle

" = 30 s atTHe-II = 0.9K

loss during diffusion

Liq.He

19KD2O

He-II

3Hecryostat

SRD220

To 3Hepump

UCN guide

UCN

detector

Spallation target

300KD2O

Graphite

Heater

1.25m

3 m

Shield of

1 m iron

0.5 m concrete

UCN

valve

UCN valve

p

n

phonon

UCN

open

annulardisk

close

Al foil

UCN loss at Al foil

1

10

100

1000

10000

100000

0 100 200 300 400

Time (0.5s/ch)

Cou

nts

/ T

ime

bin

/ C

ycl

e without annular diskwithout foilwith foil

with diskwithout foil

with foil

UCN production with a proton pulse of 60 s

1

10

100

1000

10000

100000

0 100 200 300 400Time (0.5s/ch)

Cou

nts

/ T

ime

bin

/ C

ycl

e

0.9K

1.0K

1.1K

1.2K

1.4K

Proton

UCN production with a proton pulse of 60 s

" = 30 s atTHe-II = 0.9K

protonbeam

0.1

1

10

100

1000

10000

0 100 200 300 400

Time (0.5s/ch)

Co

un

ts /

Tim

e b

in /

Cy

cle

!t = 0 s

!t =10 s

!t =20 s

!t =30 s

!t =40 s

!t =50 s

!t =60 s

Proton

"s measurement by UCN valve

THe-II = 0.9K

"s = 30 s

UCN density at 390W peak power

' = 10 UCN/cm3

UCN flow rate = 1/4·'vavS

UCN

detector

UCN

valve vav = 3.1 m/s at Ec = 90 neV

Sd = 0.52$ cm2, + = 0.68

count rate = 1/4·'vavS·Sd/S·+ = 409 counts/s

If we assume statistical distribution

1.2,106 UCN / 36 liter

Possibility at TRIUMF

' = {" $coh(Ein(E) dE} NHe )n %s0

Ec

Increasemomentum space, Ec

3/2

cold neutron flux, )n

storage time, %s

UCN transport efficiency

Increase UCN density

%s improvement

THe-II 0.9 ( 0.8 Kphonon upscattering%He-II ~ 610 s

decrease diffusion loss: x2

250 s

123 s

64 s36 s

611 s

0.8

K0.

9 K1 K

1.1 K 1.2

K

Increase storage time: x5

3He impurity ( < 1x10-11

%3He > 3890 sClean-up UCN bottle

%wall ~ 300 s

%s = 150 s

New cryostatHorizontal He-II : )n x2Ec

90(210 neV : Ec3/2 x3.6

UCN transport will be better

EpxIp 390W(20kW (duty 1/4) : )n x51

O

UCN density

5 x 2 x 3.6 x 51 x 10 = 1.8 x 104 UCN/cm3

%s horizontal

50 kWpeak: x2.5, D2O(D2: x82nd step

Additional factor : 　Loss at diffusion is suppress by

smaller loss and efficient UCN transport

p beam of 500MeV 40-A on, duty 1/4

off100 s 300 s

UCN density vs P beam power

!"#$%%

!"#$%!

!"#$%&

!"#$%'

!"#$%(

!"#$%)

!"#$%& !"#$%' !"#$%( !"#$%) !"#$%* !"#$%+ !"#$%,

-./01234.520367389:340.;/17<.=3>?@

89:3;2=A<7B3>89:C1D'@ E/03F2GHH3<=3I&E3J%=2K

E/03F2GHH3<=3I&E3&!%=2K

HLL37/0M<=23'')=2K

HLL37/0M<=23!%%=2K

HLL3M26D3F2GHH3&)%=2K

-:-3M26D3F2GHH3!'(=2K

N-H3-I&3&)%=2K

L.A3OP6D.A3-I&3&)%=2K

N8L-QOR3-I&3'')=2K

SRTGHH3-I&3&)%=2K

TRIUMF

SD2

Present

storage timegeometry

beampower

Radiation shield for 20kW/4 = 5 kW

A - A’ side view

TargetHeater

1K pot

0.4 m

vacuum

1.5 m

300 KD2O

20 K D2O

He-II

Iron

Lead

UCN

valve

1.25 m1.5 m

0.25m

0.25m

0.25m0.5 m

0.5 m

Iron floor

Concrete

Graphite

Top view

High level

room

Low level room

20KD2O

1.5m

liq. He

Iron

1.25m

3He

cryostat

2.0m2.75m

Proton beam

Heliquifier

Cryogenics

room

He-II

AA’

Roots

pump

Circulator

GM1.5m

Detector

development

EDMBeta decay

gravity

Isopure

He tank.5m

2 m2 m 2 m

1.25m

6m

5 m

Proton Hall

Target cooling

and handling

24 m

ConcreteA’

from cyclotron

TRIUMF Proton Hall

PlannedUCN site

Thanks