1. Radiation Detectors for the PSS1 at ESS
L. Johansson & P. Persson
CERN review, 1 March 2017

2. Response to comments
“The monitors will continuously monitor levels of both gamma and neutron radiation, and trip the proton beam if the radiation thresholds are exceeded.” Multiple thresholds per monitor ? Can you give the typically used thresholds ? Are there additional monitors that do not need to be SIL2 certified ? What does the abbreviation BOS (on the graph) mean ?

3. BOS
the beam-off stations consist in 46 devices placed in the accelerator tunnel whose purpose is to:
Indicate that a specific area has been searched by the patrol team (green light) prior to the start-up of the beam
Indicate that the beam is ON (blue light)
Indicate the presence of an oxygen depleted atmosphere (red light)
Stop the beam via the emergency-stop button

4. Response to comments
“The monitors shall perform  safe, long-term archiving of monitor data in databases of:
Measured values.
Events (radiation alarms, technical alarms,  system faults, etc.).
System configuration.
Providing operators with historic data from the databases for reporting or subsequent analysis.
Provide SIL2 interlock signals for the PSS1 system 
The monitors shall provide information locally within the supervised areas and will display  real time measured dose rates and alarm status.”
Shall the monitor include this function or rather a centralised system collecting the data from all monitors ?
What are these ? (technical alarms)
If referring to SIL, it should refer to the safety function not the signals ?
Could you clarify how you imagine the local setup at a monitoring location (detector, electronics, display, interfaces ...) ?
Clarification of the terminology: Of what consists a monitor ?

5. Response to comments
“Simulation/measurement results (e.g. results of Monte Carlo simulation or preliminary measurement) shall be provided for the validation of the predicted performance .” This might be hard to obtain for COTS devices. To what performance do you refer ? “The natural background radiation level is in the order of 0.2 mSv/h . “ Rather 0.1 uSv/h ?

6. Response to comments
“The company shall develop a system that complies with the international standard of IEC , IEC and with traceability to national standards.” With a dedicated development, meeting your target date for commissioning might not be feasible. Usually national standards are derived from international standards, I believe ? Which are those ? (national standards)

7. Response to comments
”AMF-002 The detector shall be able to measure ambient dose equivalent and ambient dose equivalent rate in a pulsed mixed radiation field (pulse length 5 s - 3 ms, at 1-14 Hz). The minimum measuring time shall be 0.1 s. It is recommended to use a charge digitiser for the read-out electronics. AMF-004 Under calibration conditions the variation of the detector response among all AMF detectors shall not exceed 10%.” This is a harsh constraint for commercial devices. Why would you need this ? (0.1 s) Have you checked that this is in line with the national requirements for radiation protection measurements ? (10%)

8. Response to comments
“AMF-005 It should be possible to perform calibration of the detector in-situ with a calibration source that can be positioned with high reproducibility.” Verify the terminology here: “Calibration” might be rather “validation” here ? “AMF-006 The detector should hold an internal source, e.g. 1 kBq of Am-241, for automatic temperature compensation and gain stabilisation.” Why would you need this source ? How you imagine to control the gain ? We would refrain from integrating a radioactive source in your device for several reasons: - your detector is specified to be sufficiently sensitive to deliver a signal at normal radiation background conditions; this is sufficient - handling and tracing of the sources adds an additional complication without need

9. Response to comments
It may be useful to specify the dose per pulse range; the most constraining situation being: 5 usec pulse at 1 Hz ~ 139 uGy per pulse

10. Response to comments
I suggest to relax this to measuring times starting at 1 second. For RP purposes this is largely sufficient. (see above)
100% is a high humidity level. What makes you need to set such a level ? (not in line with the requirement specified for the monitor)

11. Response to comments
Unclear what this means. Maybe you can explain more ? Are you referring to a deviation (not uncertainty) from results measured at continuous radiation ?

12. Thank you!