FNAL, May 10, Introduction for Beam Diagnostics Laboratory Main Mission: R&D on charged particle beam diagnostics for e + /e - linear colliders (ILC), other demanding e - accelerators (FELs and novel light source concepts) and proton drivers. Hardware: A small e - accelerator for ▪ in-house testing/troubleshooting of diagnostics before installing them in other accelerator beamlines (such as ILCTA at Fermilab or AWA at Argonne), ▪ training students, and ▪ doing fundamental beam physics experiments.

FNAL, May 10, Phased Plans for Beam Diagnostics Laboratory Ultimate Goal: Operate a low-average-current, multi-MeV ( MeV is possible) racetrack-microtron accelerator to drive coherent light sources. Phase 1: 6 MeV thermionic rf gun Phase 2: 6 MeV photoemission rf gun [Phase 2 beam current will be reduced compared to Phase 1] Phase 3: 20 MeV racetrack microtron (but we will go as high as permissible per our radiation shielding capability)

FNAL, May 10, Basic Design of the electron beam line Electron gun BPM FC PS Q Q Q QQ BPM – Beam Profile Monitor FC – Faraday cap Q – Magnetostatic quad 70 deg. bend PS – pumping station S S S – steering system BCM BCM – beam current monitor Adjustable slits FC

FNAL, May 10, Expected parameters of electron beam Beam Energy6 MeV Energy Spread5% RMS Normalized Emittance< 10 mm mrad Beam Peak Current10 A Beam Average Current 6  A Charge per Bunch0.44 nC Bunch Length (total)10-20 ps Bunch Rep. Rate2.856 GHz Macro Pulse Rep. Rate1 Hz Reminder: The eventual photoemission gun and racetrack microtron will operate with significantly less average beam current, i.e., ≤1 μA.

FNAL, May 10, Shielding Estimates for Beam Diagnostics Laboratory Requirement: External dose rates <1.0 mrem/hr per the administrative control levels set by DOE. Tools & Methods: NCRP Report No. 51, MARS15 Sim. Pkg. Assumptions: Maximum energy & average current Simplified geometry: removed electron gun, magnets, most of the beam pipe, maze entrance(s), supports, structural metal inside concrete walls Uniform density of all materials Initial and final energy of scattered electrons are equal (in NCRP calculation only)

FNAL, May 10, BDL shielding estimates Pb Beam stop Model layout illustrating neutron scattering, with a cubic beam stop centered 1.25 m from barrier walls BeamlineElectron gun Beam stop

FNAL, May 10, MARS15 Simulations Parameters (ref. from NCRP calc.): 60 cm concrete walls, 20 cm lead beam stop, origin of impingement placed 1.25 m from wall Results for 20 MeV, 0.06 μA beam: Normal-operating scenario: 0.08 << 1.0 mrem/hr Worst-case scenarios: ▪ ~100% of radiation impinging fwd-directed barrier wall (w/ Pb beam stop only): 1.0 mrem/hr ▪ Beam misalignment (w/ 10 cm Pb at 10 cm from beam pipe): 0.82 < 1.0 mrem/hr BDL shielding estimates

FNAL, May 10, BDL shielding estimates Absorbed Dose Rate (Gy/yr), 20 MeV & 0.06  A

FNAL, May 10, BDL shielding estimates Absorbed Dose Rate (Gy/yr) Power density, neutrons (Gy/s) Both equate to approx. ~0.02 mrem/hr ~5·10 -3 ~5·10 -11

FNAL, May 10, BDL shielding estimates Problem: MARS results are about an order of magnitude lower than those found by NCRP calculations. Why? Methodology of NCRP guidelines are inherently conservative (this is a good thing) NCRP data is inadequate to make a thorough analysis MARS input code may be incorrect Solution: Reduce margin of error in calculations (updated NCRP reports, alternate sources?) Verify MARS code

FNAL, May 10, Floor Plan of the Beam Diagnostic Laboratory Accelerating hall surrounded by concrete shielding Assembly room with clean tent and related equipment Accelerator control room Office area Laser room

FNAL, May 10, Accelerating Hall Beamline on two optical tables Sliding door “Chicane” type entrance from service areas Concrete shielding covered with lead

FNAL, May 10, Conclusions The conceptual design of the Beam Diagnostic Laboratory has been prepared The basic requirements for the radiation shielding have been established To start the actual engineering design of the concrete/lead vault the shielding specifications need to be checked by independent qualified experts