1. Jing Liu Kavli IPMU, University of Tokyo 8 Apr. 2013, Tuebingen
Measurement of Neutron Interactions with an 18-fold segmented true coaxial detector
Jing Liu
Kavli IPMU, University of Tokyo
8 Apr. 2013, Tuebingen

2. Neutron Interactions with Nuclei
X (n, n’ )
X (n, n’ )
recoil
X (n,  )
Capture
recoil
Neutron
Neutron
Neutron
Nucleus
Nucleus
Elastic
Inelastic
Neutron
Neutron
Meta-stable State
Internal conversion
Internal Conversion

3. Experimental setup

4. Cryostat and electronics
Nucl. Instrum. Meth. A 577 (2007) 574 [nucl-ex/ ]

5. Source ~ 500 neutrons / second  from de-excitation of 12C*
n energy distribution

6. Core & Segments
DAQ
Core
Any Segment

7. Core spectrum

9. Elastic Scattering or gamma escaped
X (n, n’ )
Elastic
Neutron
Nucleus
recoil
DAQ threshold n n’
Recoiling energy is very small.
Entries
Core Energy (Total energy deposited in detector)

10. Simplest Inelastic Scattering
X (n, n’ )
recoil
Entries
Neutron
Nucleus
Inelastic
Neutron
Core Energy n
Entries n’
Energy deposited in any segment

11. Simplest Inelastic Scattering
X (n, n’ )
recoil
Entries
Neutron
Nucleus
Inelastic
Neutron
Core Energy n
Entries n’
Energy deposited in any segment

12. More Complex Inelastic Scattering
X (n, n’ )
recoil
Entries
Neutron
Nucleus
Inelastic
Neutron
Core Energy n
Entries n’
Energy deposited in any segment

13. Inelastic Scattering in General
Entries
Entries E
Erecoil + E
Erecoil
Core Energy
Energy deposited in any segment

14. n+74Ge→74Ge+n’+  (596 keV ) 583 keV , Tl208 (Th232)
609 keV , Bi214 (U238)
Core
74Ge(n, n’)

15. Two more inelastic peaks

16. Recoil spectra

17. Thermal Capture Small tail X (n,  ) Capture n n’ Entries Core Energy
Neutron
Core Energy n
Entries
No notable enhancement. Decrease according to the
multi-scattering probability n’
Energy deposited in any segment

18. n+72Ge→73Ge+  (326 keV)
338 keV , Ac228 (Th232)
72Ge(n,)

19. Meta-stable State Meta-stable State n Decrease according to the
Entries
Meta-stable State
Core Energy n
Decrease according to the
multi-scattering probability
Entries n’
Energy deposited in any segment

20. n+70Ge→71mGe,71mGe→71Ge+  (198 keV)
70Ge(n,)

21. Internal Conversion Internal Conversion n n’ Entries Core Energy
Energy deposited in any segment

22. n+72Ge→72Ge+n’+e(692 keV )
72Ge(n,n’e)

23. Summary
Neutron interactions are one type of background for underground experiments
There are many types of interactions
Segmentation provides topology information of an interaction and helps identify its type
A compact detector array may have the same power