103rd ATF2 weekly meeting

International phone/webex meeting

Monalisa schedule in this summer, Andrea Jeremie (LAPP) , David Urner, Paul Coe (University of Oxford)

First, Paul presented present status and schedule as follow. The double bellows arrived and unpacked at Oxford university. wooden test frame was assembled with assembly mounting, while vacuum end boxes are being finalized in workshop. Pressure and leak tests will be completed by next Monday, 22 June. Packing for shipment in 22-23 June, and it will be collected from Oxford in 23-24 June. Paul, David and equipment will arrive at KEK in 30 June - 2 July. First vacuum test will be done on the wooden frame for 2 and 6 July at KEK. Installing the Monalisa system at ATF2-IP area for 7 and 8 July, vibration tests will be performed for 9 and 15 July. The LAPP seismic sensors will be packed for shipment in 16-18 July.

Many colleagues worry about this tight schedule. The Monalisa work has been planned by following conditions; the seismic sensors to be returned to LAPP, France by 6 August, Shintake monitor group schedule and free access in summer shutdown.

The vacuum test results must be sent via email by next Monday, since they have been requested for verification of the shipment. One concern is a lateral movement/force of double bellows. If serious problem is found, the shipment must be cancelled. Under these conditions, we agree with the presented schedule.

The system will not be back to Oxford unless there is serious modifications needed. It is the vacuum system. So, KEK will import it without exemption. In parallel, the optics system will be prepared at Oxford university. Since these two systems are independent, the latter one will be shipped to KEK in this December or January 2010.

Update of ATF2 priorities and schedule, Andrei Seryi (SLAC) , Philip Bambade (LAL/KEK)

First, Andrei presented a proposal of works and schedule during this summer and next beam run until end of January 2010. Since overseas colleagues will not be usually available in January 2009, beam runs are suggested to dedicated to ATF2 studies by end of 2009. Additional shifts are assumed from evening Friday to morning Saturday, i.e. 3 shifts/week more.

There were comments as listed below, such as check-out beam run, LW-laser to Shintake monitor, stripline BPMs and septums;

C : Number of check-out beam run day shifts is too many. The number should be three at most, since there are many site works.

Q : On "LW laser to BSM" in the last week of this December : Will UK colleagues contribute not only the laser itself but also commissioning Shintake monitor ?

A : There has been discussion on the laser performance with Shintake monitor group and Alex. We need more discussion on collaborative works including commissioning among them. In this summer, UK group will come to KEK for the LW laser system installation. So, it must be good opportunity.

C : In this summer shutdown, laser transport line will be prepared from the LW laser to Shintake monitor. There are lots of works in order to use it, e.g. replacement of optical mirrors for higher intensity, better timing system for short pulse ( to 0.3ns from the present 8ns ) and alignment etc. . Apparently, the first priority is to commission the interference mode in this year.

Q : It is very nice for SLAC (LCLS) to produce electronics of stripline BPMs. Will SLAC also commission the electronics system at KEK ?

A : SLAC already received drawings of BPMs and will study them for designing. SLAC can participate remotely in commissioning at least.

C : The BPMs suffer from the kicker noise which degrades the performance as Yves showed undesired intensity dependence. Therefore, SLAC engineers should come to KEK in order to study such environment before finalizing the design.

C : Yves studies show that one long and small aperture (80mm long, 24mm dia.) stripline BPM (MQF9X) near the second kicker (KEX2) has strange behavior while the other 3 same type ones (MQF13,14,15X) are good. Also, 5 short and large aperture (40mm long, 40mm dia.) BPMs have different intensity dependence, which are located at upstream of BH2X. 3 short and small aperture ones are located between BH2X and KEX2.

C : Assuming the intensity dependence is generated by residual pedestals due to kicker noise at each electrodes, we can estimate these 4 parameters by measured data, i.e. ADC data of 4 electrodes per BPM. Of-course, the pedestals must be very small in case of good calibration.

C : There are 3 issues in readout of the stripline BPMs. (1) calibration pulses are different from real ones, while they are resembled, (2) existence of kicker noise and (3) different ADC gate timing of MQF9X. Since all of DR BPM electronics will be replaced in the shutdown, ADC modules will be available for optimum gate timings to all BPMs. So, the third issue becomes irrelevant.

C : Also, there is beam intensity issue. The beam intensity has been low, i.e. less than 0.5 x 10¹⁰/bunch with which Yves has analyzed data. Since the electronics has been designed with the intensity of more than 1 x 10¹⁰/bunch, we should study with such high intensity.

C : The electronics is based on clipping technique ( by Schottky diode ) to extract the negative parts which are input to ADC-modules. Therefore, upgrade of clipping circuit is a relevant issue in this summer shutdown. Actually, 9 BPMs ( from MQF1X to MQD8X ) have the same electronics of head amplifier and clipping circuit, and the last 3 BPMs ( MQF13X,-14X and -15X) have the clipping modules II labelled LOW GAIN.

C : We have 6 QBPMs as spares. In principle, they are available if the electronics is provided. In general, QBPM is more robust against the kicker noise for the resonance cavity and digital circuit.

C : As we saw, there are 5 stripline BPMs with 40mm aperture at upstream of BH2X, while the total number of stripline BPMs is 12. Can we use the c-band QBPM with 20mm aperture for them ? Also, we have to check spaces to install QBPMs.

Q : Are there field-mapping measured data of septums ? If not, can we measure them in this summer?

A : No, there is no measurement. The measurement is difficult since we do not have device.

Q : How much is the rotation estimated for large vertical dispersion ?

A : It is 4mrad at the septum-C, i.e. the last one. It is 17mrad at the septum-A.

Q : Can we measure such rotation of septums ?

A : Yes, we can do with tilt monitor.

KEK site meeting

We discussed on plan in this summer shutdown, i.e. IP screen monitors, knife edges and necessary modification for the LW laser to Shintake monitor. In addition, measurement of temperatures around the detector was reported as a function of time after the PMT-HVs were turned on. Also, the gain monitor system was reported.