1. neutron lifetime experiments
higher order processes
(2 W- exchange, photon production, …
 “radiative correction”)
tn determines l
need other measurements to separately determine gA and gV. These are the basic parameters that determine Hw .
Feb 2008
E. Beise, P441 notes

2. neutron lifetime experiments
Two techniques:
1) beam: send neutrons through a well-defined volume,
determine the “loss rate” by counting decay products:
decay product
rate into a
detector
# neutrons incident on the
defined volume
2) “bottle” or “storage”: trap neutrons, measure decay products vs time.
other loss mechanisms
Feb 2008
E. Beise, P441 notes

3. NIST Center for Neutron Research
20 MW reactor is source of “cold” neutrons: Tn ~ eV
deBroglie wavelength:
reactor core
Feb 2008
E. Beise, P441 notes

4. Cold Neutron Research Facility (Guide Hall)
Feb 2008
E. Beise, P441 notes

5. NIST lifetime experiment (beam type)
Feb 2008
E. Beise, P441 notes

6. NIST lifetime experiment (beam)
Feb 2008
E. Beise, P441 notes

7. UCN lifetime experiment on NG6-U
Feb 2008
E. Beise, P441 notes

8. neutron lifetime measurement at ILL (Grenoble, FR)
UCN trap
A.P. Serebrov, etal
cryostat
UCN’s in
Feb 2008
E. Beise, P441 notes

9. summary of measurements
Serebrov, etal
Feb 2008
E. Beise, P441 notes

10. UCNA experiment, Los Alamos Experimental Method
from J. Martin, U. Winnipeg
Endpoint energy 782 keV
Focus electrons onto detectors using a strong (1 T) magnetic field
Feb 2008
E. Beise, P441 notes

11. UCNA Experiment, Los Alamos
from J. Martin, U. Winnipeg
Feb 2008
E. Beise, P441 notes

12. Ultracold Neutrons: Superthermal Process
slide from C.-Y. Liu, Indiana Univ.
R. Golub and J. M. Pendlebury, Phys. Lett, A53, 133 (1975)
Cold neutrons downscatter in the solid, giving up almost all their energy, becoming UCN.
UCN upscattering (the reverse process) is suppressed by cooling the moderator to low temperatures.
Feb 2008
E. Beise, P441 notes

13. UCNA experiment UCNA Experiment commissioning underway
slide from B. Filippone, Caltech
UCNA experiment
Experiment commissioning underway
Initial goal is 0.2% measurement of A-correlation
(previous measurements ~ 1% uncertainty)
UCNA
Liquid N2
Be reflector
LHe
Solid D2
77 K poly
Tungsten Target
Feb 2008
E. Beise, P441 notes

14. Los Alamos prototype UCN source
slide from A. Young, NCSU
Liquid N2
Be reflector
Solid D2 (5K)
77 K poly
Tungsten Target
58Ni coated stainless guide
UCN Detector
Flapper
valve
LHe
SS UCN Bottle
5 K poly
PhD Thesis: Chen-Yu Liu, Princeton Univ. , (now faculty at Indiana U)
Feb 2008
E. Beise, P441 notes

15. Experimental Area B: UCNA Experiment
beta-spectrometer magnet
From UCN
source
beta detector
polarizer magnet
“prepolarizer” magnet
UCN
guide path

16. UCNA spectrometer
Feb 2008
E. Beise, P441 notes

17. Slide from P. Mumm, U Md, 2007
Feb 2008
E. Beise, P441 notes

18. Slide from P. Mumm, U Md, 2007
Feb 2008
E. Beise, P441 notes

19. emiT detector assembly
from P. Mumm, 2007
Feb 2008
E. Beise, P441 notes