Minutes of ATF2 weekly meeting, 29 June, 2011

June 29 15:00 - 16:00 (JST time), Webex and ATF LC meeting room, KEK

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Scheduled talk of Y.Renier is postponed to next week.

Status of ATF Operation, T. Okugi

In last week, the cavity Compton group commissioned the detector in the DR. The beam intensity was limited up to 0.5 x 10¹⁰/bunch due to temperature rise. It was difficult to stably operate the cooling water system at the LINAC, especially in daytime so that the ATF beam was unstable.

Cleaning the chiller system for the water cooling, the cooling power increases. So, the beam intensity can be raised to 0.7 x 10¹⁰/bunch in this week.

FONT work, P. Burrows

Oxford university group was working since last Friday in order to checkout the FONT system. Now, the BPMs and cables are all working. We found some cables which have been broken by shielding concrete ceiling blocks at the earthquake. They were replaced. We are seeing strange effects in the stripline BPMs which may be due to circuit-short. It is now checked by network analyzer. We will remove the BPMs to insect in details if needed.

First quick Sensor Evaluation for Ground Motion Detection and Feedforward, A. Jeremie

From Yves's study on the feed-forward system to correct ground motion (GM), the extraction and final focus beam lines in the total length of about 90m must be equipped with significant number of GM sensors. From Sugahara-san's measurement in the DR, 2006, the sensor should be needed in every 4m since the coherence is lost for about 4m ( 22 sensors in total ) . Recent Yves's study, ALCPG 2011, shows that more than 20 sensors are needed for good correlation between jitter corrected displacements and estimated GM effects.

For the GM measurement at ATF2, the sensors must have frequency range from 0.1Hz to 50Hz ( to 100Hz better), magnetic field resistant and radiation hard.

We looked into prices and delivery time for DAQ (20,000 to 30,000 euros) and various types of sensors such as accelerometer, velocimeter and geophone ( 1,200 to 5,000 euro/sensor) . The delivery of sensors is 3 months.

We (LAPP) has 50,000 euros in total, which must be spent by 5 November, 2011. Taking account of the delivery time, we have to order them early in July, 2011, it is now. We need to decide what we should purchase.

Q : How much low frequency must be measured by the sensors?
A : If the ATF is operated at 6Hz, it must measure down to 0.5Hz at least.
Q : The ATF is operated at 1.5Hz now. So how much in this case ?
A : We need to measure even lower frequency, say 0.1 Hz.
Q : Since the DAQ is expensive, is there other alternative choice ?
A : We need vibration measurements and to analysis them. We need one such system for 20 sensors.
Q : Can you purchase the sensors first, and the DAQ later ?
A : Yes, it is possible.
Q : You had better to discuss with Daniel, since CLIC has some priority for selection of sensors.
A : Yes, I see him in this Friday. Anyway, we must order them before 15 July, 2011.

IPBPM progress on the impedance issue of the digitizer, S. Boogert

We are discussing a mitigation plan with Glen. The signal reflections can be removed by software. However, the hardware solution is more preferable.

C Glen : We will study this issue at the test stand, SLAC. It should be checked out in a week.

Next meeting is 6th July, 2011.