Minutes of the Linac4 Diagnostics Working Group Meeting held on 10 March 2008

Present: E.Bravin, C.Dutriat, J.Tan, U.Raich, F.Lenardon, K.Hanke, E.Sargsyan, M.Eshraqi, A.Lombardi, B.Dehning, L.Soby, A.Lokhovitskiy, B.Mikulec.


1. Communications

2. Follow-up of open actions

3. BLMs in Linac4 and in the new transfer line

4. AOB

2. Follow-up of open actions


-. D-plate design: The design for a movable diagnostics bench for Linac4 commissioning is advancing. U.Raich will give a presentation at the next meeting. It might be possible to use the slit method for the emittance measurement for the Linac4 part, but the energy deposition after the Linac4 exit would be about 10x the one at Linac2 energies. FLUKA simulations are needed to determine the final solution; maybe the ATB group can help there. The emittance measurement unit should in any case be retractable and should maybe always be done at much reduced beam power.

-. EVM document and budget breakdown per year: The EVM document has not yet been prepared. Concerning the budget breakdown U.Raich has communicated to M.Vretenar that for 2008 50k CHF are required for Linac4 diagnostics (excluding the budget for the 3 MeV test stand). This money is mainly needed for the development of the readout card of BI equipment (CERN ADC card).

-. CERN ADC card: One prototype card is available and under test and one module submitted for production. Test software is under preparation.


-. Alignment: M.Pasini explained in an email that the alignment is currently planned to be done with a 'clavette', where the alignment of the quadrupole is done mechanically. Due to the small size of the quadrupole it is difficult to install arms for the alignment targets. The phase pick-up is then mounted directly on the quadrupole, and the alignment should be performed with respect to the magnetic axis.
A.Lombardi said that the quadrupoles will all be aligned with respect to their mechanical axis to avoid aperture restrictions.
It was felt that more information was needed on this subject (in particular the alignment of the pick-ups). B.Mikulec will invite the Linac4 alignment specialist M.Jones for one of the next meetings.


-. BLM rack space: The BLM rack space request has been transferred to C.Rossi and accepted. U.Raich said that currently all 20 BI racks are concentrated in one location. This seems not to be an ideal situation (mainly due to varying cable length), but it might still be possible to be changed.

3. BLMs in Linac4 and in the new transfer line

The main issues in the BLM discussion concern the final location of the BLMs and their sensitivity. The question whether the sensitivity of the BLMs is sufficient at low energies requires detailed FLUKA simulations. B.Dehning mentioned that B.Holzer had a meeting with V.Vlachoudis to ask for support on this subject, but he wasn't aware on the outcome of the discussions.

A.Lombardi said that they want to be able to detect <1% losses for the nominal beam current. To be able to cope with this it might be necessary to use neutron detectors at low energies instead of BLMs (need FLUKA simulations to decide). The cost for a neutron detector that can be bought off the shelve seems to be comparable to the cost for a BLM.

F.Lenardon and L.Soby stated that the transformers should be able to detect differences of beam current at the 1% level. For the placement of the BLMs it would therefore be an option to take also the position of the transformers into account.

In general, losses will occur mostly at the transition between tanks, at aperture limits and at the location of high dispersion. For the moment, BLMs are foreseen at each transition region between tanks. For the new transfer line BLMs should be added in vicinity of the bendings and quadrupoles, but the exact location requires further simulations. In the meanwhile, the first beam loss simulations from M.Eshraqi could be helpful. The BLMs should be placed close to the beam; ideal would be a distance of 0.5-1 m.

Assigned to Start date Description State Result
K.Hanke 2008-03-10 Define preliminary location of BLMs in the new transfer line in high dispersion regions. Done. edit

B.Dehning informed us that the development of the Linac4 BLM electronics has been started by a technical student; the work consists in modifying the LHC electronics to the Linac4 requirements.

4. AOB

The next meeting will take place only in 3 weeks (March 31st) to avoid a clash with a BI section meeting. The aim is to hold the Linac4 Diagnostics WG meetings always during odd weeks.

-- BettinaMikulec - 10 Mar 2008

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Topic revision: r3 - 2008-06-30 - FrankGerigk
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