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

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

Experimental setup

Cryostat and electronics Nucl. Instrum. Meth. A 577 (2007) 574 [nucl-ex/0701004]

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

Core & Segments DAQ Core Any Segment

Core spectrum

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)

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

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

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

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

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

Two more inelastic peaks

Recoil spectra

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

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

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

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

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

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

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