1. Radiation fields During 1st stage beam commissioning
Lali Tchelidze
AD Safety Group for the ACCSYS Project
Critical Design Review of Radiation Monitors for the PSS1
March1, 2017

2. 1st stage beam commissioning layout

3. ESS war linac Warm linac: Ion source LEBT RFQ (3.6 MeV) MEBT
DTL (90 MeV) - commissioning planned up to DTL tank 4 (75 MeV)

4. Sources of radiation Sources of ionizing radiation:
Proton beam losses (assumption 1 W/m during normal operation, full beam loss during worst accident)
Proton beam on commissioning beam dump
X-rays from RF conditioning

5. Proton beam losses

6. Calculation geometry model
N. Mokhov et al.

7. Radiation fields in the tunnel
Normal operation: 1 W/m from five DTL tanks
N. Mokhov et al.

8. Radiation fields in the klystron gallery
Normal operation: 1 W/m from five DTL tanks
Total prompt dose rate < 1.2 μSv/h
Accidental full beam loss
Total prompt dose rate < 120 mSv/h
N. Mokhov et al.

9. Radiation fields in the front end building
Normal operation:
1 W/m from five DTL tanks and RFQ
Total prompt dose rate < 0.1 μSv/h
R. Bevilacqua

10. Proton beam on beam dump

11. Radiation fields outside shielding chicane
Beam parameters will be chosen such that the total dose rate outside of the shielding chicane is < 3 μSv/h.
K. Batkov

12. Radiation fields at various steps of 1st stage beam commissioning
K. Batkov

13. Radiation fields at various steps of 1st stage beam commissioning
K. Batkov

14. Radiation fields at various steps of 1st stage beam commissioning
Commissioning beam parameters will be chosen to respect 3 μSv/h at accessible areas during beam on.
K. Batkov

15. X-rays during RF conditioning

16. Radiation fields during RF conditioning
X-rays are expected as RF power is applied to accelerator components
No estimates/measurements exist at this stage
Assumption is that X-ray field is fully attenuated with the shielding designed for neutrons

17. Q&A
Do you need/want to monitor both sources of radiation ? With the same or different detectors? It is mandatory to monitor neutron field. I think it could be valuable to monitor X-rays as well, to gain confidence that they are truly fully attenuated by the shielding.
2 GeV - This is only for the full PSS so not part of the scope of this document? Correct. Thus only radiation fields relevant for PSS1 is presented and discussed here.
It would be meaningful add the max. expected dose per pulse (including the pulse length and repetition rate). Depending on commissioning mode (fast beam, slow tuning beam, etc.) we can always make quick scaling.
Are these the maximum expected levels for the ‘Condition’ ? What would be the associated alarm thresholds in these areas? Maximum expected levels are reported during beam commissioning, not RF conditioning.
What is the reason for the changing g/n ratio for Zone 1 and 2 ? First of all, the ratios are very approximate. The reason for changing the ratio is because the neutron production starts at the end of RFQ, at energy MeV.
Is this referring only to the photon component accompanying the neutron field or is there another gamma/X-ray source? Usually we call gammas, the photons associated with the proton beam and X-rays, the photons associated with RF power.
Although your proton beam goes up to 75 MeV, your moderated and scattered neutron spectra may not be that highly energetic. Do you have radiation spectra at the monitoring locations ? If the neutron energies are below 20 MeV this might relax the requirements for the detector. We don’t have particle spectra.
The continuous/quasi continuous is X ray only and coming from RF ? Is it limited only to the klystron gallery above the accelerator tunnel ? Yes, usually we call X-rays, the photons associated with the RF.

18. Thank you!