# Presentation: 396422

## SD2 UCN Source Performance at LANSCE

- A. Saunders, T. Bowles, R. Hill, G. Hogan, K. Kirch, S. Lamoreaux, C. L. Morris,
- A. Pichlmaier, S. Seestrom (*Los Alamos National Laboratory)*
- S. Hoedl, C.-Y. Liu, D. A. Smith, A. R. 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, T. Kawai** (***University of Kyoto)*
- A. Serebrov (*Petersburg Institute for Nuclear Physics)*

## Solid D2 Spallation UCN Source Concept

- SD2 source †
- SD2 has  a large downscattering rate R
- Cold SD2 is predicted to have small absorption and upscattering cross sections-> long UCN lifetime 
- UCN density, R, is predicted to be large.
- Spallation driver‡
- High cold neutron density
- Shutter source
- †R. Golub and K Boning, Z. Phys. B **51, **187 (1993).
- ‡A. Serebrov, “First UCN Factory Workshop’” Jan 18-22, 1988, Puskin, Russia.

## Estimated density

## 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

## Line C Measurements

*Line C Measurements*

- UCN
- Detector

- Cold Neutron
- Detector

- Proton
- Beam

- Line C results show reduced ( 100) UCN production.
- D2 frost on guide windows and walls.
- Gravity+Aluminum detector window

## Solid D2 in a “windowless” container

- Grown from a gas phase at 50 mbar

- Cooled through the triple point

## First Blue Room Run

*First Blue Room Run*

- Improved cryogenics
- Good signal from solid D2.
- Low backgrounds, especially at long times of flight.
- UCN production still very low!

## July 1999 Blue Room Runs

- Liquid N2

- Be reflector

- Solid D2

- 77 K poly

- Tungsten Target

- 58Ni coated stainless guide

- UCN Detector

- Mr flapper

- LHe

- Predicted lifetime from D2:
-  = V D2/VD2
-    = ~18 s

## Life time summary

- Significant UCN fluxes are produced from 50 cm2 SD2.
- SD2 lifetime looks shorter than expected even for 10 K up-scatter cross section.
- Temperature?
- Other up-scatter mechanisms?

## 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.

## UCN setup in line B at LANSCE

## SD2 Lifetime Measurements

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

## Temperature dependence (20 cc .02 para-deuterium)

*Temperature dependence (20 cc .02 para-deuterium)*

- 

- 

## Ortho-para dependence (4.5-6 K)

*Ortho-para dependence (4.5-6 K)*

- Data

- Monte Carlo

- Data

- 

- 

- 

## Bottle measurements

*Bottle measurements*

## 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.

## High current runs (heating)

- 24 **Coul

- Volume=100 cm3
- 	  =200 cm3
- Para-deuterium fraction=.02
- T = 5.29 K

## World Record UCN Density 6/29/00 

- 

## Beam Heating Effect

- Temperature (K)

- Time

## Future Uses for Prototype

- Confirm lifetime and other physics measurements
- Test bottles, UCN guides
- First experiments with new source
- Beta spectrum
- Neutron lifetime in magnetic bottle
- Test run at AGS?

## Source plans: commission the LD2 pit and Area B at LANSCE

- Shielding
- Power
- Water cooling
- Cryogenics
- Proton beamline

*Source plans: commission the LD2 pit and Area B at LANSCE*

## Conclusions

- We have successfully tested the new source at LANSCE.
- We have observed stored UCN densities of over 100/cc, the highest in the world.
- UCN production and lifetime depend on para contamination and temperature as expected.
- Work continues to optimize full scale source design and experiments!