Neutron Capture cross section barns Thermal Neutron capture

Neutron Capture cross section [barns] Thermal Neutron capture by 10 B Element • B isotopes in dielectric, packaging or as substrate doping • n capture by 10 B creates an highly ionising a particle • Most n captures in 10 B are around Maxwell peak where En ≈ 0. 025 e. V

The 10 B(n, a)7 Li reaction Thermal Neutron Capture • Both the a particle and the 7 Li recoil can upset a memory cell • 90% of these events are from n with En < 15 e. V • 95% of these events are from n with En < 60 e. V → we will have many low energy n in the LHC underground areas

Reducing the SER from thermals • Eliminate the BPSG layer between the silicon and the metallization layer metal layer BPSG n+ p+ p p+ n Si Substrate “old” electronics • Apply shi metal layer PSG n+ p+ p p+ n Si Substrate “new” electronics • Shielding package for individual components on a PCB : § Boron nitride (B 4 C) with polyimide layer § Mold compound with BPSG filler instead of normal silica § …

Radmon SRAM memories x-sections 512 k by 8 bit configuration 32 pin functionality 3 -5 Volt powering plastic Toshiba TC 554001 FL-70 L 9827 0. 5 mm Toshiba TC 554001 AL-70 L 9929 0. 4 mm Thermal 8. 7 e-15 2. 7 E-15 (1) 2. 5 E-15 (2) (1) Measured with NPL laboratories Teddington UK D beam on Be target using runs with and without cadmium (2) Measured with PROSPERO reactor in thermalised n spectrum With and without cadmium Fast 8. 4 e-15 7. 8 e-15 1. 1 e-14