Minutes from REX meeting 2005-06-16

Present: Mats Lindroos (chair), Fredrik Wenander, Georgi Georgiev, Nikolai Trofimov and Pierre Delahaye

General

* The minutes from the last week were approved.

* The 70Se run finished on Monday evening. The users were overall content. A performance report of the run is found in a separate document on this page.

* David Porret will be invited for the next meeting to report on the consolidation progress and the implementation of the vacuum system into the control system.

* There are two candidates for the short term replacement of Thomas Sieber when he departs.

* Georgi inquired about the breakdowns of power supplies in the Linac line during the run and what is done to prevent similar incidents in the future. Nicolas David is presently revising all the supplies and improving their connections.

* Georgi will move the ionization chamber from the second to the straight beam line. Thus it can be constantly installed without interfering with other setups in the second beam line.

Thomas is absent from 16/6 until 4/7 (incl)

Fredrik is absent from 18/6 until 29/6 (incl)

REXTRAP and REXEBIS

* The target group has been asked to add Rb as surface mass marker in the two coming targets for the Ni/Cu and Sn runs, on top of the Ni, Cu, and Sn mass markers for the lasers.

* Profile pictures of the beam in the BTS should be taken using the MCPs. This will act as reference for future ion injection into the EBIS this year.

* The recently noted high trap efficiency (>50%) should be verified with careful measurements and TOF controls. Shallow and normal trap potential configurations should be compared.

* The REXTRAP GUI should be let running continuously with different operation conditions (scope, picoamp, dummy etc) to see what provokes the crashes so this can be avoided in the future. Romain should start the development of a new GUI asap.

* Romain and Nicolas David will improve the correspondence of the set and readback values in the control programme for the BTS section.

* Romain will look into why the readback values of the REXTRAP HT are jumping in time.

* The emittance meter is being dismantled and shipped back to LMU.

* One of Pierre’s summer students, Åsa, will carry out mass resolving measurements with the REXTRAP.

* The EBIS motor-generator will be stopped in August for investigation of the starting up problems.

* The ‘TOF’ out of the EBIS using the RFQ.BO30 MCP has successfully been tested. It can as predicted be used to measure the extracted charge out of the EBIS for a single A/q.

* The weak signal in RFQ.BO30 was due to a misalignment of the insertable Al plate into the beam. The chamber has now been rotated and the MCP response is improved significantly. The correct voltages are: MCP gain 1800 V; Acceleration potential 3500 V; Phosphor voltage 4000 V.

* The readout of BTS.FC150 and SEP.FC80 are still unstable for high currents (>1 nA). Mats has been asked to contact Enrico Bravin from the BD group about the problem.

LINAC

* The plans for the work on the rf-system while Thomas is away are the following:

- The high voltage transformer from the RFQ amplifier will be removed this week and shipped back to Munich on Friday for modification.

- One of the two modified HV trafos will be installed before the next REX run

- Additional measurements will be done next week to find the reason for the permanent reflections from the cavity. Besides this, the amplifier has to be made less sensitive to short peaks in the reflected power signal. Han will discuss with Berdermann if one can install a "pulse reduction" for this. It exists in Linac3, so it should be feasible at REX as well.

- At the same time he will discuss the possibility to send the 200 MHz amplifier back to Munich, so Berdermann can do the necessary repairs on the rf-cavity at his own workshop.

- We found that we have to buy one additional oscilloscope (5kCHF) on the REX budget

- If the problem with the reflected power is once solved, there might be another series of measurements on the dummy load (with the 200 MHz) in the week after next week

to determine the maximum duty cycle (which is, as you know, limited by the heating problem). At the moment, anything higher than 20 Hz, 500 us at 90 kW results in switch offs each 1-2 hours.

- Munich was asking for a list of items for their BMBF rf equipment account (19 kE), otherwise the money might be blocked or used for something else. We plan to buy another spare tube (14 kE), another spare HV transformer (4 kE), and a pulse generator (1 kE) on the T229800 and told this to Munich.

- There is still air coming out at the ventilation system in the amp room, although they said they closed the slots. It might be the best if the rf-workshop simply produces some sheets to close them once for all (except 2 of them).

* The slow pumping down of the RFQ section could maybe be due to air pockets in one of the quadrupole lenses in front of the RFQ cavity. The drawings should be investigated and possibly the section being opened up during next shutdown for optical inspection.

Controls system etc

* The beam diagnostics FEC has been working satisfyingly since the complete reinstallation of the software last Friday. Sylvestre Catin has been asked to look into some still remaining network problems on the console computers in the control room.

* Nikolai T will carry out some tests with the new PLCs for the beam optics control during this micro shutdown. Thereafter he will test the new controls for the RF.

* Mats has contacted an external programmer to investigate if he could implement the slow extraction of ions from the EBIS. The work should be supervised by Joakim Cederkall. Fredrik pointed out that it is not only a question of programming but also work with the hardware to find the problems with the jittering timing and the malfunctioning vector writing to the GFAS timing modules. This programmer could possibly also do the application programmes for the new control system.

Minutes taken by Fredrik Wenander