1 / 5

Neutron damage of DSSDs

Neutron damage of DSSDs. Neutron irradiation. 5. Nakayama-san expects ~ 100 MeV neutrons However, the rate is still 10 11 /cm 2 /year! ~10 12 /cm 2 during Belle II lifetime! near the type inversion (but needs proper scaling...). Neutron background. Neutron energy is around 5MeV. 3.

hall-lee
Télécharger la présentation

Neutron damage of DSSDs

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Neutron damage of DSSDs Manfred Valentan (HEPHY Vienna)

  2. Neutron irradiation 5 • Nakayama-san expects ~100 MeV neutrons • However, the rate is still 1011/cm2/year! • ~1012/cm2 during Belle II lifetime! • near the type inversion (but needs proper scaling...) Manfred Valentan (HEPHY Vienna)

  3. Neutron background Neutron energy is around 5MeV. 3 Manfred Valentan (HEPHY Vienna) • Neutron from radiative Bhabha • Gammas from radiative Bhabha event will propagate along beam axis and hit the beam pipe/magnet iron at ~10m downstream, then coming back to Belle. Main source of KLM neutron BG. Scales with luminosity (KEKBx40), we should increase the shields in tunnel. • Neutrons generated in Touschek loss shower • Touschek particles hit the beam pipe at s=~1m (inside detector) • More dangerous, because generated very close to detector and almost impossible to shield . • Showers generated by 4GeV e+ hitting beam pipe consists of high energy neutrons(~100MeV) • Beam tests so far is done at ~370keV. • Any sub-detector using Si or readout FPGA might be affected.

  4. Assuming no stopping power by detector materials, 0.9GHz e+  at 1m away, ~104/cm2/sec neutrons  at 1m away, ~1011/cm2/year neutrons (PID group assumption: 1011/year/cm2) (Radiation test at Yayoi, 370keV: 1012/cm2) 0.9GHz e+ LER e+ At 1m away, ~1011/cm2/year of ~100MeV neutrons 2m Neutron energy is around 5MeV. 3m • Thanks to the additional collimators, the neutron flux are now comparable to the PID estimation (1011/cm2/year), but the neutron energy is much higher (~100MeV, not 370keV). • Detailed neutron spectrum will be given by GEANT4 full simulation soon. 4 Manfred Valentan (HEPHY Vienna)

  5. Neutron damage • Even the corrected background simulation results predict considerable neutron damage • Neutron dose seems to be too high • near type inversion „feels“ unplausible • Please ask Nakayama-san if neutron rate is really 1011/cm2/year! • If so, we must still be very careful and think about a neutron irradiation test! Manfred Valentan (HEPHY Vienna)

More Related