68th ATF2 meeting

1. Investigation of a crack in the ATF2 floor, N. Terunuma

In last December, shallow cracks have been inspected by making a hole at a crack. Typical depth is 10cm where there is no iron structure.

More information can be read in an above note.

Q : How thick is the concrete floor ?

A : The detailed information can be obtained in Terunuma's presentation on "CF and schedule" at the 5th ATF2 project meeting. A 0.6m thick concrete slab of 396m³ is supported by 0.6m thick beams and 38 piles with 0.7m diameter and 13m height.

Q : Did the cracks develop after the floor was painted?

A : No, the floor paint was on the cracks. Since end of October, there is no new crack developed. So, it seems that the cracks were developed while the surface dried up as the company has expected.

Q : What is future plan for cracks ?

A : The hole will be covered. Periodically, the crack will be inspected inside the hole. New inspection-hole will be made if necessary.

Sugahara has plan to measure GM across the cracks.

2. Beam Extraction by using Strip-line kicker with Pulse Bump Orbit, Takashi Naito (KEK)

A stripline kicker of 30cm length and 24mm gap has been tested at DR to excite the bump. Observing the kick angle as a function of pulse-timing, the rise time of pulse was estimated to be 3ns. The pulse height was 5.8kV and the maximum kick angle was 0.18mr .

Present kicker system has 4.6mr kick angle. New system has 2.6mr by fast kickers with 10kV pulser, where there are two stripline kickers with 60cm length, 12mm gap. So the new stripline kicker system needs a local bump and an auxiliary septum magnet to bend enough for extraction.

In total 7 correctors are needed for bump orbit at DR, and they were installed. The local bump will be tested soon, i.e. in January 2008. The septum design was completed. The leakage field was estimated to be less than 10Gauss at the central filed of 0.1T. The fabrication will be completed by March 2008. The beam extraction will be tested in Spring 2008.

We do not know how it is stable for ATF2 . So, the Spring run is just for test.

Q : How much is the stability?

A : 10^-4 stability of the pulser for DC power supply (semi-conductor).

Q : How much is the stability of timing ?

A : The timing is also stable, since jitters have been measured by kick-angles. Page.6 shows the jitter meas., where error bars can shows 30ps and 100ps in flat top.

Q : How can be the septum cooled ?

A : Like as the PEP-2 magnet, stainless cooling pipes are used.

Q : Since the current density is very high, it must be difficult to work.

A : The septum has 12mr kick angle with 900 A and 10mm gap.

Q : cooling in vacuum ?

A : Yes, the magnet is inside of vacuum.

Q : It is difficult to work at PEP2.

A : I heard the difficulty. we got a lot of information. In the company, a realistic design has been started .

Q : Since the engineering is difficult, we (SLAC) welcome questions .

A : Stainless cooling water pipe is difficult. If we use square cooling pipe as in PEP2, 3mm square cooling pipe is necessary. A round pipe will be used. I will send you (C.Spencer) the detailed design for reviewing.

3. Operational procedures for HA PS, Briant Lam (SLAC)

SLAC group is preparing a description of technical benefits for near-term SLAC and US projects from development of the High Availability power supplies for ATF2.

In order to realize these benefits, we (SLAC) would need to get certain information from ATF2 operation, which may require establishing some procedures. The draft list is written in above htm file.

C : The ATF control system records all currents whenever they are changed. It is possible to record them every in 2 minutes. Also, it is easy to access the recorded data.

Q : What is the recording timing ?

A : It can be cyclic ( depending on frequency ) or whenever they are changed.

Q : Is there failure reporting system in the ATF control system?

A : It has been usually written in the LOG books.

Q : Is there any electric document ?

A : No at present.

Q : I recommend to have it for MTF can be specified. Electric-LOG system can be used for this purpose, too.

C : We would like to ask KEK colleagues for suggestions/proposals to realize the electric documentation in the ATF control system.