Takeyasu ItoUniversity of Tennessee

EDM Collaboration meeting August 19-20, 2004

Nature of a Separate Production Cell

• What dimensions are appropriate and what UCN density can be achieved?

• What fill time for the production cell (4 liter) will be required with a 1” aperture connecting pipe?

• What should be the time for the ultra-pure helium to become contaminated with 3He?

Takeyasu Ito 2

ModelMeasurement cell

Production cell

Connecting tube

Beam

Parameters•Measurement cell volume: Vm= 7cm x 10cm x 50cm = 3500cm3

•Connecting tube cross sectional area: Atube = (2.5/2)2 = 5cm2

•Production volume length: Lp=100 cm•Production volume cross sectional area: Ap=20cm x 20cm = 400 cm2

•Beam cross sectional area: Abeam= 10cm x 10cm = 100 cm2

•UCN production rate: Rp= 1 ucn/cm3/sec•UCN velocity: vucn= 600 cm/sec•Cell lifetime: cell = 1200 sec•Neutron lifetime: beta = 886 sec

Takeyasu Ito 3

EquationsWhen the valve is closed:

ddtVmnm

1

1

cell

Vmnm

ddtApLpnp AbeamLpRp

1

1

cell

ApLpnp

When the valve is open:

ddtVmnm

1

1

cell

Vmnm vucnAtube

4np nm

ddtApLpnp AbeamLpRp

1

1

cell

ApLpnp vucnAtube4

np nm

Takeyasu Ito 4

ResultsU

CN

den

sity

nm

np

Valve opens at t=2500 s

Time (s)

np0 Rp p

tot AbeamAp

nm0 np

0 VpVp Vm

pfill p

tot

Takeyasu Ito 5

ResultsU

CN

den

sity

nm

np

Valve opens at t=2500 s

Time (s)

mfill

4VmvucnAtube

Takeyasu Ito 6

Summary• UCN density in production cell

• Production cell fill time

• UCN density in measurement cell

• Measurement cell fill time

• In order for nmsep~nm

combined, Vp»Vm

• If pcell > m

cell, then perhaps nmsep > nm

combined possible

np0 Rp p

tot AbeamAp

pfill p

tot ~ 500s

nm0 np

0 VpVp Vm

mfill

4VmvucnAtube

~ 5s