Summary of radiation shielding studies for MTA Muon production at the MiniBooNE target Igor Rakhno August 24, 2006

An accident scenario Prompt dose at normal operating conditions Groundwater contamination with tritium Residual activation Fermilab-TM-2248 (2004) Fermilab-TM-2305-AD (2005)

Plan View

Beam & Target Beam: 400-MeV protons; σ r = 1cm 2×10 14 p/s or 1.3  p/pulse at 15 Hz repetition rate Proton interaction lengths, λ (cm) Targets Target L (cm) R (cm)% of λ tot LH Cu LH 2 Al Cu λ tot λ inel

Spallation neutron studies → full absorption (≈100%) targets of heavy & dense materials (Pb, U nat ) are used. It is claimed that the facility can serve as a multi- purpose one for future operations. The 1-cm thick copper target (10% of interaction length) is considered as a generic (modest “averaged”) target.

Muons, Inc.

Accidental beam loss Deflection upward due malfunction of upstream magnets as high as 50 mrad (for 8-GeV proton beam accidents at Fermilab booster a deflection angle of about 1 mrad is usually considered). Duration of an accident ~ a few minutes. Calculated dose rate on the top of the berm = mrem/s = 1 mrem/min = 60 mrem/hr.

Calculated dose rate on the top of the MTA berm at normal operation

Dose Equivalent in the Access Pit (normal operation) Lower Level Upper Level

Dose Equivalent in the Cryo Room (normal operation) 10´´ penetration 4´´ and 8´´ penetrations

Neutron Energy Spectra in the 10 ´´ Penetration Near target hall Near cryo room

Beam absorber and groundwater activation

Conclusions With the current beam absorber design the groundwater contamination with tritium does not exceed the EPA limits. The existing berm–10.5 ft soil–allows to run at rep.rates significantly lower than 15 Hz. It is a matter of choice/money – run at low intensity for a long time or build a local shielding and run at high intensity. Significant local shielding around the RF test cell (Muons, Inc.) is required to irradiate the cell at maximum beam intensity (rep.rate). Alternative – running at low rep. rate ~ 1 pulse/min. The penetrations between the target hall and the cryo room is a problem. Extra local shielding is required.

Muon production at the MiniBooNE target

Muon spectrum behind the absorber (at 54.5 m) 8-GeV protons on Be 2.5×10 13 p/s In the range of MeV ≈ 10 2 muon/cm 2 ·sec