1 How Many Protons can we afford to loose in the PS ? Thomas Otto SC-RP

Th. Otto SC-RP How many protons can we afford to loose in the PS ? PS/SPS Days Conceptual Framework of Modern Radiation Protection Exposure to radiation must be justified. We assume that this is the case for duly approved research projects at CERN Dose to personnel and public must be optimised Every reasonable effort (technical or organisational) to reduce the exposure must be taken (ALARA) Legal Dose limits must not be exceeded

Th. Otto SC-RP How many protons can we afford to loose in the PS ? PS/SPS Days Some derived limits and thresholds Dose equivalent at fence: H*(10) < 1.5 mSv/a Action Level for personnel working at CERN: H p (10) < 6 mSv/a (15 mSv/a in present code) Excess needs detailed study, justification, and written authorisation Exposure of non-radiation workers at CERN should not exceed 100  Sv/a

Th. Otto SC-RP How many protons can we afford to loose in the PS ? PS/SPS Days At the heart of the issue: Intensity 2006 (proj.) CNGS request per year (1998: WANF) PS delivers in multiturn extraction … plus, for FT programme Total

Th. Otto SC-RP How many protons can we afford to loose in the PS ? PS/SPS Days Multiturn Extraction Beam is “cut” on a septum blade Important losses in septum (ss 16) Further losses in ss 9 and ss Total losses in PS amount to nearly 20% in 2006 – as much as extracted in 2004! Display of PS beam loss monitors during multiturn extraction

Th. Otto SC-RP How many protons can we afford to loose in the PS ? PS/SPS Days Radiological consequences of beam losses Stray radiation – “skyshine” exposes personnel working at CERN and public Activation of air The PS is not ventilated sytematically as e.g. the SPS. Air is escaping uncontrolled This topic is not addressed here, but will not be forgotten Activation of accelerator components shortens lifetime of these parts exposes maintenance personnel

Th. Otto SC-RP How many protons can we afford to loose in the PS ? PS/SPS Days Weakness of PS The PS is not designed for the intensities accelerated today Nowadays, such accelerators are built underground (e.g. FAIR at GSI)

Th. Otto SC-RP How many protons can we afford to loose in the PS ? PS/SPS Days PS Bridge Weakest part of PS shielding 180 – 340 cm of concrete Important beam loss point : ss9 ≈ 100 m from fence If the full beam was lost, a dose of several mSv in a single supercycle would result The free passage over the Bridge will be blocked Crane will only pass Bridge, when PS stopped These measures also satisfy safety requirements for increased doses on the PS Bridge from “normal” losses Effect on workshops in North Hall: ≈ 3  Sv/h. Only suitable for work on activated material

Th. Otto SC-RP How many protons can we afford to loose in the PS ? PS/SPS Days Multiturn extraction vs. environmental doses Projected dose at PMS 128: H*(10) = 1.9 mSv/a Persons working in buildings nearby (PS Centre) will receive dose in excess of 100  Sv/a Optimisation = Relocation of personnel

Th. Otto SC-RP How many protons can we afford to loose in the PS ? PS/SPS Days Dose at the fence Dose rate measurement during CNGS MD p/h extracted 0.09  Sv/h neutron dose + 50% for  and  At p/a: approx. 800  Sv/a Below limit, but no safety margin left

Th. Otto SC-RP How many protons can we afford to loose in the PS ? PS/SPS Days Activation of Accelerator PS Ring Survey Dose rate measured in 40 cm distance at both ends of a straight section After CNGS MD, increase by a factor ≈ 2 compared to other years Decrease by ≈ 30% in 10 days If this is not sufficient, longer waiting time before shutdown work

Th. Otto SC-RP How many protons can we afford to loose in the PS ? PS/SPS Days Collective dose during shutdown p/year H coll (man- mSv) No strong correlation Collective dose depends on amount of work Heavy ion runs helped to reduce doses Obviously, increased losses will lead to increased doses during maintenance

Th. Otto SC-RP How many protons can we afford to loose in the PS ? PS/SPS Days Short-term interventions E.g. change of a septum during the run Increased losses = Increased dose rates on equipment = longer waiting time before intervention is possible This can only be planned case by case in the optimisation process The availability of new (inactive) spare parts would help

Th. Otto SC-RP How many protons can we afford to loose in the PS ? PS/SPS Days Conclusions With the planned beam for CNGS, at present loss levels, the PS will reach (or may exceed) its intensity limitation Once CNGS takes up full intensity, numerous consequences: Relocation of certain offices and workshops Close monitoring of dose at fence Waiting time before and time limitations during interventions and maintenance

Th. Otto SC-RP How many protons can we afford to loose in the PS ? PS/SPS Days How the AB dept can help Decrease the losses Work on Island Extraction scheme is encouraged Every proton accelerated should be “justified”. Don’t accelerate for the dumps! Improve Beam Monitoring BLM system as in SPS or LHC would allow better observation of losses, and prediction of activation, and, ultimately, doses Optimize intervention and maintenance operations Better planning Provide spare parts

Th. Otto SC-RP How many protons can we afford to loose in the PS ? PS/SPS Days Last but not least: DG address to staff, progress in consolidation of PS and SPS importance of safety issues to limit individual and collective radiation doses. Improvement is necessary in the future on the handling of safety constraints and work efficiency