# Presentation: 905152

## Status of the Prototype UCN Source

- A. Pichlmaier, S. Seestrom, W. Teasdale (*Los Alamos National Laboratory)*
- S. Hoedl, C.-Y. Liu, D. A. Smith, A. Young (*Princeton University)*
- B. Filippone, T. M. Ito, J. Martin, B. Tipton, J. Yuan (*California Institute of Technology)*
- P. Geltenbort  (*Institut Laue-Langevin)*
- M. Hino** (***University of Kyoto)*

*Status of the Prototype UCN Source*

- Description of Source Operation.
- Recent Measurements in Line B
- Comparison to Calculations
- Predictions for Area B Source

## Recent Source Measurements

- Volume Scan Shows Saturation
- Bottled UCN
- Up to 30 UCN/cc using 10 pulses over 5 seconds
- Lifetime Measurements
- As a function of deuterium temperature
- As a function of para-D2 contamination
- Proton Current Scaling
- Linear up to the maximum current so far
- Effect of Solid D2 Quality

## UCN Source Layout

- Liquid N2

- Be reflector

- Solid D2

- 77 K poly

- Tungsten Target

- 58Ni coated stainless guide

- UCN Detector

- Flapper
- valve

- LHe

- SS UCN Bottle

## Volume Dependence

## Bottled UCN

- 0

- 200

- 400

- 600

- 800

- 1000

- 0

- 5

- 10

- 15

- 20

- 25

- Time (sec)

- UCN/8 ms

- 8 Proton Pulses

- 0.5 s Storage Time

- Emptying Bottle

- 17.5 UCN/cc
- 24 C in 8 pulses

- 20k UCN above BG

## Bottle Density Corrections

- 0.01

- 0.1

- 1

- 10

- 0

- 1

- 2

- 3

- 4

- 5

- 6

- 7

- 8

- 9

- 10

**time (s)**

**neutrons/cc/uC**

- calculations x 0.75

- 200 cc SD2, 0.2% HD, 2% para

-   at 5 K

- input valve closed at 0.5 second

- Vmax=8m/s

- Vmax=16m/s

- Vmax=30m/s

- no exit

- exit open at 4 s

- Without extrapolation to peak density,
- correction is 3.18.
- Vbottle=3640 cc

## UCN Lifetime in Solid Deuterium

- Nuclear absorption in SD2 cannot be avoided
- Lifetime is 150 ms
- Other sources of UCN loss can be controlled
- Lattice phonon absorption (150 ms at 5 K)
- Nuclear absorption on hydrogen (150 ms at 0.2% H)
- Conversion of para-deuterium (150 ms at 1% para-D2)
- Lifetimes add as resistance: 1/=(1/1+1/2)
- Total lifetime is then about 40 ms.

## SD2 Lifetime Measurements

- UCN trapped in “bottle” with SD2
- Valve opened to release UCN at different times

## UCN Lifetime in SD2

- Minimum and Maximum measurable lifetimes:
- Minimum because it takes time to drain UCN
- Maximum caused by bottle lifetime

## Para Contamination’s Effect

## Proton Current Scaling

## Beam Heating

## Solid D2 in a “windowless” container

- Grown from a gas phase at 50 mbar

- Cooled through the triple point

## Volume Dependence

- 0

- 200

- 400

- 600

- 800

- 1000

- 1200

- 1400

- 1600

- 0

- 50

- 100

- 150

- 200

- 250

- 300

- 350

**SD2 volume (cc) **

**UCN/10^12 protons**

- REH 4/12/00

- calculations x 0.75

- 0.2 % HD

- 5 K

- 2 % para

- 1 % para

- Measured

- Runs 1847-1941

- MT run = 1847

- no aperture

- Transport Model does not include flapper valve, details of bottle.

## UCN Detection Time

## Future Uses for Prototype

- Continue lifetime measurements
- Other source materials
- Oxygen
- Nitrogen15
- Lead208
- Test bottles, UCN guides
- First experiments with new source

## Conclusions

- We have successfully tested the new source at LANSCE.
- We have observed stored UCN densities of up to 30/cc.
- UCN production and lifetime depend on para contamination and temperature as expected.
- Work continues to optimize full scale source design and experiments!