Targets/Meetings/2012-10-05

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Friday 5th October from 11:30am–12:30pm. Quick meeting in David Jenkins office R2 4.09. Stephen Brooks and Tristan Davenne also in attendence.

Actions

  • David Jenkins
    • ✓ Information on Ta cladding stress for Bernie Riemer of SNS
      • ✓ Stress limits from hipped pure Ta sample test
      • ✓ Modelling results from Chris Densham's group
    • ✓ Entries for ISIS targets in target parameter table
  • Stephen Brooks
    • ✓ Contact Steve Roberts (Oxford materials) about analysing non-irradiated hipped Ta-clad W sample
    • ✓ Notes from HB2012 target session (see below)
    • ✓... Ask Chris Warsop about radiation damage to ISIS graphite collimators (reduction of thermal conductivity?)
  • Tristan Davenne
    • ✓ Contact engineers involved in ISIS Ta-W target hipping process regarding collaboration with Chris Densham's group. [Dan Wilcox from CD's group will do a placement with ISIS regarding the hipping process, most likely after Christmas.]
    • ✓ Forward work done on TS1 studies to David Jenkins.

HB2012 Target Session Notes

-- Long Baseline Neutrino Experiment (LBNE) Target Material Radiation Damage Studies Using Energetic Protons of the Brookhaven Linear Isotope Production (BLIP) Facility (N. Simos, BNL)
Graphite can handle thermal neutron radiation to tens of DPA but energetic protons less than 1 dpa
BNL BLIP target has many layers of material with 181MeV p going in and 112.6MeV p coming out the other end
Thermal simulations with energy deposition seem to give good agreement with reality (e.g. LBNE target test)
Different graphite grades differ significantly in their response to irradiation
Non-destructive testing can assess damage effects during annealing

-- Radiation effect modelling at intensity frontier: status and uncertainties (N. Mokhov, FNAL)
MW beam domain gives ~0.1MJ/g and up to 1TW/g specific energy and power densities
MARS does magnetohydrodynamics?
Integrated cross sections in most current codes agree to within 10% with data, but double differential cross sections can be 2-3x out (need more data)

-- Understanding ion-induced radiation damage in target materials (M. Tomut, GSI)
A heavy ion leaves a trail (track) of defects along its path
Phase diagram of graphite/diamond etc. is interesting
Sensitivity to track formation is measured as a keV/nm threshold (~1 for polymers, oxides; ~20 for semiconductors; ~50 for metals)
Raman spectroscopy along the ion trajectory shows different structures at different depths (elastic vs. inelastic collision regions, some glassy phase)
Used a cantilever to detect swelling on upper layer, produces bending
Graphite thermal diffusivity (mm^2/s) suffers under irradiation, worse for lower irradiation temperatures (even 1500C down to <1/3 of pristine; 600C down to ~1/25)
Pulsed beam of same integrated intensity broke the sample
These ion-induced effects are different from neutron irradiation
Steep degradation of material properties once the ion tracks start to overlap
Running graphite at >1000C extends lifetime due to defect recovery

-- Discussion (accelerator system design, injection, extraction and beam-material interaction)
1W/m is really only applicable from 100MeV and up: DTL and RFQ are different; elsewhere it is very widely applicable
Sand bags are excellent shielding material (used at FNAL D0 for two decades)
But in high radiation environments the the bag itself gets damaged
New ROOT-based geometry in MARS sounds useful (compatible with LHC detectors!)
- Supports repeated sub-assemblies
Nik Simos: hope for "wonder materials" is on nanoscale amorphous structures that eat defects
Bruce Brown (FNAL): high-strength steel can suddenly fail from chloride embrittlement
M. Tomut: don't have to use pure graphite; looking at graphite reinforcement at the nanoscale, for instance ITER have looked at titanium nanoparticle-reinforced graphite.  Unfortunately ions still form tracks (e.g. in iron-boron) in this materials and cause embrittlement, so application dependent.
> Can ISIS extract at intermediate energies?  (Energy dependence of cross-sect)
PASI Targets Meetings
2012 May 1st Kick-off meeting · August 7th WP1 · October 5th WP1 · October 9th Universities/modelling · December 5th WP1
2013 January 29th WP1 · February 28th Universities/modelling · April 3rd–5th PASI annual workshop ·

December 5th Third General meeting

2014 September 9th Fourth General meeting