radiation protection studies for the hie isolde post-accelerator
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Radiation Protection Studies for the HIE ISOLDE Post-Accelerator. A. Dorsival, S. Giron, Joachim Vollaire on behalf of DGS-RP. Outline. Introduction Post-accelerated beams in ISOLDE today (before LS1) Increased radiological hazards with HIE-ISOLDE - PowerPoint PPT PresentationTRANSCRIPT
Radiation Protection Studies for the HIE ISOLDE Post-Accelerator
A. Dorsival, S. Giron, Joachim Vollaire
on behalf of DGS-RP
Outline Introduction
Post-accelerated beams in ISOLDE today (before LS1)
Increased radiological hazards with HIE-ISOLDE Shielding analysis for the new post-
accelerator Definition of the source term FLUKA calculations and shielding integration
Maximum dose rate due to ion beam losses RP monitoring Conclusions and Perspectives
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Post-accelerated beams in ISOLDE today Current (warm) post-accelerator:
Already a source of X-ray with a max. energy of 400 keV (concrete + lead shielding)
Neutron energy ~ 3 MeV/amu below the Coulomb barrier (threshold value for nuclear reaction to occur)
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Post-accelerated beams in ISOLDE today RF interlock (captured key) prevent access
during RF operation RP measurements inside and outside the Linac
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Pos 1: 186 mGy/hPos 2: 7 mGy/hPos 3: 700 mGy/hPos 4: 1.5 mGy/h
Dose rate outsideless than a few mSv/h
Increased radiological hazards with HIE-ISOLDE
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Beam A/q Energy (MeV/u) Intensity (ppA) Comment
? 2 19.8 1 Radioactive beam (limit case)
Ne5+ 4 11.3 4 Stable pilot beam
N4+ 3.5 12.6 5 Stable pilot beam
He2+ 2 19.8 10 Stable pilot beam
He 4 11.3 1000 High intensity stable beam
1 pnA = 6.25e9 ions/s
EDMS 1325812HIE-ISOLDE Safety Review 05/11/2013
Cavity number Peak voltage (kV) Comment
IHS 1 325 Max. 10 % duty cycle
7-gap 3 260 - 277 Max. 10 % duty cycle
9-gap 1 410 Max. 2.5% duty cycle
Low-Beta cavity 12 585 CW
High-Beta cavity 20 900 CW
X-ray emitting devices
(Radioactive) Ion beams
{Existing
{New
EDMS 1227549 (D. Voulot)
Sta
ndard
beam
Exceptional (emittance measurements)
Shielding for the new post-accelerator
6
Constraints & Challenges: Accelerator inside the experimental hall Consider space constraints and services necessary define the source term !!!!
Strategy: Review of existing facilities (Legnaro, Triumf…) Measurements of X-ray emitted by prototype
cavities Conservative approach to extrapolate the
maximum dose rate with the operation of several cavities in parallel
FLUKA calculations with a detailed layout of the shielding enclosure to identify possible weaknesses and access restrictions EDMS 1325812HIE-ISOLDE Safety Review 05/11/2013
Dose
Rate
mG
y/h
Measurements of X-ray
7
Measurements performed on prototype cavities tested in SM18 (CERN) and IPN Orsay
Dose
Rate
mG
y/h SM18 IPNO
Conclusions: Hundreds of mGy/h during He processing Few tens of mGy/h during normal operation
EDMS 1325812HIE-ISOLDE Safety Review 05/11/2013
1 Gy ~ 1 Sv
Dose
Rate
mG
y/h
Normalization for shielding calculations
8
Test bench in SM18 implemented as a FLUKA geometry
Starting randomly electron (900 keV = max. energy) in the ion beam plane
Normalization to the measurement results to obtain the electron emission rate
350 mGy/h
I0= 8 x 1013 pps
For 350 mGy/h at themonitor location
EDMS 1325812HIE-ISOLDE Safety Review 05/11/2013
HIE-ISOLDE Safety Review 05/11/2013
FLUKA calculation for the shielding
EDMS 13258129
Detailed FLUKA geometry of the tunnel (penetrations, door…)
No access to the vault during RF operation (as today) Design objective for the bulk shielding, remain below
1mSv/h due to X-ray from the cavities
Lead window
Access door
Penetration “chimney” (steel)
Results of FLUKA calculations
10
Starting 600/900 keV (low/high beta) electrons using the normalization factor derived from the SM18 conditions with He processing in all cavities (pessimistic)
Normal RF operation/conditioning dose rate should be lower by more than a factor 10
EDMS 1325812HIE-ISOLDE Safety Review 05/11/2013
Horizontal Cut at beam height – He Processing (all cavities)
Results of FLUKA calculations
11
Many penetrations on the roof (empty in the geometry) Locally hundred of mSv/h on the roof during He processing
BASELINE : NO ACCESS TO THE ROOF DURING RF conditioning /He Processing and RF operation
Could be relaxed if measurements show acceptable levels
EDMS 1325812HIE-ISOLDE Safety Review 05/11/2013
Post-Accelerator shielding status
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Lateral concrete blocks have been delivered and installed
Still assessing the strategy for the up-beam shielding (1 cm of lead today) and the possibility to implement the final shielding for Phase 2 later Repeat dose rate measurement on “production” cavities (possible safety margin)
EDMS 1325812HIE-ISOLDE Safety Review 05/11/2013
Dose rate in case of (stable) ion beam losses
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He 19.8 MeV/amu He 12 MeV/amu
Example full beam loss of 1 ppA (dipole magnet)Full beam loss of 1 ppA (profile)
Stable pilot (10 ppA /20 MeV/amu):• 130 mSv/h full beam loss (He)Emittance meas. (1 pnA/11.3 MeV/amu):• 2 mSv/h full beam loss (He)
Exclusion area for emittancemeasurements
HALLACCESSIBLE
HALLACCESSIBLE
Radiation monitoring
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Replacement of ARCON monitor by RAMSES monitor launched during LS1 Increase the monitoring of the low energy beam lines in case
of RIB losses (Gamma Radiation Monitoring System GRAMS) Monitoring specification take into account the post-
accelerator operation and the high energy beam lines
EDMS 1325812HIE-ISOLDE Safety Review 05/11/2013
+ 2 XRM above
Conceptual specification XRM (X-ray monitor) for pulsed x-ray
AMF (Area Mixed Field Radiation monitor) suitable for (n,g)
Local alarm units
Radiation monitoring integration
1
2
3456
7
8
9
10
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Conclusions and perspectives
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Comparison with existing facilities to determine that X-ray was the main hazard to consider for the tunnel Effort to assess maximum dose rate for different cavity operation
phases Conservatism in the approach used : maximum energy for the e-,
performances of prototype, all cavities conditioned in parallel…) Ion beam intensity much lower than what is used in ISAC2
(TRIUMF) with the hall accessible to users The RP monitoring has been specified accounting for X-ray
monitoring and higher beam energies Existing hazards and corresponding RP procedures will remain
(contamination risks when opening the vacuum system and dose rate in case of strong gamma emitters beam loss or collection)
Future studies to assess the activation/RIB implantation for beam intercepting device (waste studies….)
EDMS 1325812HIE-ISOLDE Safety Review 05/11/2013
Acknowledgements
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A. Bernardes, R. Catherall, M. Fraser, J. Hast , Y. Kadi, S. Maridor, J. Mildenberger, I. Mondino, B. Nicquevert, D. Parchet, E. Siesling, M. Therasse, A. Trudel, G. Vandoni, W. Venturini , D. Voulot…..
EDMS 1325812HIE-ISOLDE Safety Review 05/11/2013