Linac-4 Diagnostics review closeout

1. Linac-4 Diagnostics review closeout

2. Are the technical choices presented sound and are they likely to meet the requested specifications? • Emittance measurements • Proposed system is likely to meet the requirements at 3MeV • Sufficient distance between the slit and harp should be provided • We recommend to have a permanent in-line emittance measurement system in the chopper line • The system looks expensive for a temporary diagnostics. The slit design could have been simpler.

3. Are the technical choices presented sound and are they likely to meet the requested specifications? • Beam current transformers • Proposed system is likely to meet the requirements but 1% of absolute is challenging • We suggest to verify noise immunity in the lab and at the test stand • Effect of dark current from a nearby cavities is a concern. WE recommend to verify experimentally as soon as there is an opportunity

4. Are the technical choices presented sound and are they likely to meet the requested specifications? • Beam Position Monitors • We are not sure the proposed system is likely to meet the requirements in the linac, where BPMs are close to the RF cavities. It should be OK in the transmission lines. • We suggest to estimate or measure interference level from the cavity RF field and optimize choice of operational frequency • We think that achieving 1% accuracy for beam current measurements is difficult due to dependence on bunch shape, energy, BPM aperture. Difficult calibration will be required. • We recommend to add a broad band output for monitoring beam current modulation due to chopper

5. Are the technical choices presented sound and are they likely to meet the requested specifications? • SEM grids and wire scanners • Proposed system looks OK from mechanical design standpoint and data acquisition electronics • Consider using carbon wires in the transfer lines if it allows to do measurements with full length pulse • We have serious concerns regarding the possible cross-talk between the wires due to stripped electrons • In case of SEM grids there is no enough experimental experience with H- beam. Test could be done at SNS or other facilities. • In case of wire scanner there is a solution: to spread wires far apart or to use separate horizontal and vertical systems • We recommend to consider other types of non-interceptive measurements: ionization profile monitor, luminescence monitor and a laser wire • The overall cost looks high

6. Are the technical choices presented sound and are they likely to meet the requested specifications? • Beam Loss Monitors • We are not convinced that the proposed system is likely to meet all the requirements everywhere • Below 50MeV ionization chambers are not sensitive enough and adding neutron detectors is recommended • Combining fast protection functions and residual activation measurements looks complicated • X-ray background from the RF cavities is a concern • Reaction time of the protection of 5us needs to be justified • Every quadrupole magnet downstream of the DTL should have an ionization chamber and additional movable detectors should be planned • The required dynamic range looks extremely large • The cost looks very reasonable

7. Are the technical choices presented sound and are they likely to meet the requested specifications? • Injection region • It’s in initial stage of design, hard to predict success • Consider if measuring H0 and H- going to the dump is really necessary • The choice of the camera looks expensive, especially if lifetime will be short

8. Are the technical choices presented sound and are they likely to meet the requested specifications? • Software • We do not feel to be experienced enough to give comments on software design • In general the required software is similar to other CERN diagnostics and we do not expect problems

9. Are the technical choices presented sound and are they likely to meet the requested specifications? • Bunch Shape Monitor • Proposed system is likely to meet the requirements • Thermal emission could be a limiting factor for the dynamic range

10. Are the technical choices presented sound and are they likely to meet the requested specifications? • Halo Monitor • It is very interesting device. Very high dynamic range and time resolution have been demonstrated. • We think it will be difficult to achieve 10^-5 dynamic range in real beam line due to background from thermal emission, vacuum stripping etc. • It appears that the requested dynamic range is not really justified • This is a test device. A permanent chopper monitor should be envisioned

11. Are the technical choices presented sound and are they likely to meet the requested specifications? • Laser profile and emittance • Proposed system is feasible but in an early stage of the design • Do not underestimate the required efforts to build the infrastructure: laser room and transport line • Use of diamond detector is interesting but consider more conventional methods as well

12. Are the number of instruments and their proposed locations sufficient to cover LINAC4 needs • Add a Beam Phase Position Monitor to the chopper line • Add a dedicated chopped beam waveform monitoring system • Equip every quad in the beam line with a loss monitor • Consider an in-line emittance device in the chopper line

13. Other general considerations? • Inconsistent requirements for sensitive electronics location: • BCM , SEM grids pre-amps are in the tunnel • BLM preamps are outside