Test Beam Experiment T-489 Measurements of Induced Activities and Residual Dose Rates J. Bauer, V. Bharadwaj, H. Brogonia, A. Fasso, M. Kerimbaev, J. Liu, S. Rokni, T. Sanami, J. Sheppard, H. Tran (SLAC) M. Brugger, S. Mallows, S. Roesler, H. Vincke (CERN)

Motivation Strong activation of beamline components and surrounding environment at LCLS (e.g., dump) and future Linear Colliders (e.g., beam delivery system, positron target, and beam dumps) elevated residual dose rates – dose to personnel activation of environment (groundwater, soil, air) – dose to population activation of material – production of radioactive waste structural damage of materials – degraded machine performance, repair Optimization of design is essential to keep impact on personnel, facility operations and decommissioning, and environment (and associated costs) ALARA Monte Carlo codes are used to predict induced activity but: lack of experimental data for benchmarks (FLUKA, MARS, GEANT)

Goal Provide experimental data to benchmark activation predictions for electron accelerators by Monte Carlo codes First benchmark of a new method to calculate residual dose rates with FLUKA at an electron accelerator Combined benchmark of induced radioactivity and residual dose rates Benefit from similar, limited experiments performed at SLAC and a hadron accelerator (CERN)

Monte-Carlo calculation: LCLS 13.64 GeV, 5 kW electron line Elevation view Elevation view NEH NEH FEE FEE 13.64GeV, 5kW 1 mrem/h 10 mrem/h 100 mrem/h 0.1 mrem/h 0.01 mrem/h 1 rem/h Prompt dose rate 13.64GeV, 5kW 1 mrem/h 10 mrem/h 100 mrem/h 0.1 mrem/h 0.01 mrem/h 1 rem/h Prompt dose rate By MARS15 Geometry plotter By MARS15 Geometry plotter concrete Elevation view iron Residual dose rate concrete Elevation view iron Residual dose rate 13.64GeV, 5kW ± Ground water activity System failure Analysis

ILC Positron Target Activation J.Sheppard, V.Bharadwaj Preliminary calculations using FLUKA shows activation levels in range of 100 R/hr inside tunnel Remote handling needed Need good estimation of the activation field of the target hall * too high leads to over-design and increases construction costs * too low lead to operational risk and loss of performance Can use FLUKA to design shielding to reduce activation fields in the target hall, reducing construction costs, operational costs and operating risk Experimental benchmarking of FLUKA (and other codes) critical for believable estimation of activation Schematic for Remote Handling Concept for ILC Positron Source Target Station

Hadron Accelerator Activation Study One experiment was conducted at ESA by SLAC-RP and results were published in NIM (2002), which identified several improvements needed in measurements and Monte Carlo codes. Several benchmark studies were performed at hadron accelerators (CERN) during the past five years (collaboration between SLAC and CERN RP-groups) Results have triggered model developments with impressive improvements for hadron machines (from factors of 2-5 in the past to ~20% at present) Wide and successful application of these models for Large Hadron Collider studies, proof of model performances was requested by supervising authorities This SLAC benchmark study will be performed in complete analogy !

Accelerator Activation Study - References SLAC: S.Rokni, A.Fasso, T.Gwise, J.Liu, S.Roesler Induced radioactivity of materials by stray radiation fields at an electron accelerator Nuclear Instruments and Methods in Physics Research A 484 (2002) 680-689 CERN: M.Brugger, A.Ferrari, S.Roesler, L.Ulrici Validation of the FLUKA Monte Carlo code for predicting induced radioactivity at high-energy accelerators Nuclear Instruments and Methods in Physics Research A 562 (2006) 814-818 M.Brugger, H.Khater, S.Mayer, A.Prinz, S.Roesler, L.Ulrici, H.Vincke Benchmark studies of induced radioactivity produced in LHC materials, Part I: Specific activities Radiation Protection Dosimetry 116 (2005) 6-11 Benchmark studies of induced radioactivity produced in LHC materials, Part II: Remanent dose rates Radiation Protection Dosimetry 116 (2005) 12-15 J.Vollaire, M.Brugger, D.Forkel-Wirth, S.Roesler, P.Vojtyla Calculation of water activation for the LHC Nuclear Instruments and Methods in Physics Research A 562 (2006) 976-980

Hadron Accelerator Activation Study – Specific Activities Ratio FLUKA/Exp 0.8 < R < 1.2 0.8 < R ± Error < 1.2 Exp/MDA < 1 R + Error < 0.8 or R – Error > 1.2

Hadron Accelerator Activation Study – Residual Dose Rates

Machine Requirements for T489 Momentum: 28.5 GeV/c Intensity: > 109 / pulse (approximately 100 W at 10 Hz) Space: approximately 1 meter along beamline Beam monitoring: accurate record (<10%) of integrated intensity and history profile Beam alignment: relative alignment to target within about 1 mm Duration: 16 shifts, 3 shifts per day (5 1/3 days)

Resources Equipment: Manpower: beam dump (SLAC, available) supports for dump and samples (SLAC) material samples (CERN) beam intensity monitoring (SLAC, available) dose rate instruments (CERN / SLAC, available) gamma spectrometry (SLAC, available) Manpower: 1 CERN student, Marie-Curie Fellowship Programme 3 CERN RP staff physicists 3 SLAC RP+ILC staff physicists 2 SLAC RP technicians