97th ATF2 weekly meeting

International phone/webex meeting

Beam size measurement by Shintake monitor, Yoshio Kamiya (ICEPP, The University of Tokyo)

Y.Kamiya studied performances of two methods for modulation depth (=M) estimation, which are using curve fitting (method-1) and using minimum/maximum points (method-2). In case of Gaussian beam profile with no jitter, they should agree.

First, the beam sizes were calculated in case of non-Gaussian profiles. G.White and R.Thomas have simulated beam sizes with the nominal and pushed-beta optics, respectively. The simulated one has a core Gaussian and a tail broad distributions. In case of the nominal optics, the calculated size has slightly larger by 1nm than the core size (37.2nm) systematically. In case of the pushed-beta optics, the calculated one is larger by 4nm than the core of 23.7nm. Distributions of the calculated beam sizes are similar to the ones of core beam size for each case. This means that the monitor measures a size which strongly corresponds to the core beam size for these profiles of two optics case. There is no significant difference in the calculated distributions between the two estimation methods.

Next, two methods were compared in case of Gaussian beam with two kinds of jitter, which are the intensity jitter (A) and the interference fringe jitter (B). Major results show that the method-1 is robust against A (5 to 15% jitter) while the method-2 is robust against B (5 to 15nm jitter) as expected.

Jitter sources were estimated as follows;

• jitter-A with corrections
  1. detector resolution = 7.5%
  2. beam intensity = 1%
  3. beam timing = 4%
  4. laser power = 1%
  5. laser position = 0.5%
  6. laser timing = 0.7%
  7. total = 9%
• jitter-B with corrections
  1. phase jitter = 13.5nm
  2. beam jitter = 8.7nm
  3. total = 16nm

Q : What results are expected for more distributed beam profile ?

A : If such profiles are available, we can study.

C : We may see jitter origin, e.g. A or B or both, from both results of method-1 and 2.

Background measurements at ATF2, Marc Verderi (LLR - Ecole polytechnique) , Hayg Guler (LLR Ecole Polytechnique, France)

First, motivations of background studies were presented as follows. Some of background sources are common with ILC such as beam halo and beam gas scattering, and backscattering of particles ( neutrons ). Common tool can be applied in order to simulate/study them both at ILC and ATF2 beam-lines. The tool is BDSIM based on GEANT4. It can be experimentally verified at ATF2.

Beam halo can be studied around LW signal area and Shintake detector area, where we can measure background generated at upstream wire scanners too. In front of beam dump, backscattered &gamma and neutrons can be measured with TOF information. Especially, various physics models predict different distribution of neutrons in BDSIM/GEANT4, which would be discriminated.

The detector consists of pure CsI and plastic scintillators. It should be adaptable configuration with multiple layers and lead absorbers, and also compact for easy relocation. It will be built in November and December 2008 and will be calibrated somewhere ( LLR, DESY, Saclay, KEK?) in December and January. It can be transported to KEK by February 2009.

Finally, a list of possible study plan was presented with shift requirements.

C : The proposal should be presented for approval at the TB/SGC meeting in December, while it seems to be reasonable. It can be submitted at the ATF homepage, i.e. http://atf.kek.jp/collab/ap/about/index-new-program.php.

A : Yes, we will do.

Q : Does your machine time is parasite or dedicated ?

A : As explained in the list, it has both. We do need dedicated runs.

Proposal of QM7R replacement etc. , Philip Bambade (Laboratoire de l''Accelerateur Lineaire (LAL) (IN2P3) (LAL))

The QM7R ( 32mm diameter aperture) replacement proposal was presented. The extracted beam goes through at 22.5mm off-center of QM7R, where K1L becomes smaller by 24% and K2L appears to generate significant x-y coupling. We found three TOKIN 3581 quadruopoles with aperture of 42mm diameter. In this magnet, the K1L and K2L error is expected to almost disappear, which should be checked. Therefore, possible action plan was shown, i.e. magnetic measurement of TOKIN 3581 and also its calculation, modification of supports, two QM7's for symmetry in the DR and possible schedule of replacement. The replacement would be better in early January, 2009.

Quick measurement of magnetic field in QM14R1, Mika Masuzawa(KEK)
file, ppt, pdf(4 pages, 872kB)

The magnetic measurement actually started with Hall probe. TOKIN 3581 has been used as QM1R1 with the maximum current of 235A (29.9A/m ). First measurement was B_y as a function of x at 100A ( 14.7T/m). The gradient is less by 5% at 22.4mm off-cencter.

Q : How much current is needed at the nominal operation ?

A : It would be 146A by scaling from 131A at QM7R, bore diameter from 32mm to 42mm and different coil turn number.

Q : Do we need the excitation curve ?

A : Yes, and also we need the effective length.

First idea for a quadrupole whose basic parameters could satisfy need for a larger aperture quad where QM7R sits, Cherrill Spencer(SLAC)
file, ppt, pdf(5 pages, 148kB)

In order to have the 22.4mm off-center extracted beam go through the linear section of the field, a quadrupole magnet with aperture of 60mm diameter at least would be required. Also, the overall length should be less than the 120mm length of QM7R. Satisfying these dimensional requirements and the field strength requirement, existing quadrupole magnets with aperture of 80mm diameter were found at SLAC, called a "3.15Q2.375". Style has 10cm effective length and the operating current of 402A gives 20T/m while present QM7R has a gradient of 21.3T/m. The availability to borrow of these 2,currently un-used, quads must be asked to SLAC colleagues.

Q : How much is the cooling water pressure?

A : It was designed to run at 200PSI, which is about twice at nominal one at ATF, i.e. 85 PSI. NOTE ADDED LATER: Because the aperture of the proposed replacement quad is so much bigger than the present QM7R, the effective length of the 3.15Q2.375 quad is much longer than QM7R's and so the gradient needed to reach the same integrated strength of 16.173kG is smaller . The current needed to produce the smaller gradient is 324 amps, with 85 psi delta pressure the 3.766Kwatts of power can be cooled with a 10.5 degree C temperature rise. So this style quad could be run with the present ATF2 water pressure.

KEK site meeting

Progress of Shintake monitor work, Takashi Yamanaka (The University of Tokyo)

Participants : Terunuma, Tauchi, Kamiya, Oroku, Yamanaka

1. Installation status

Cabling is now on going. It will be finished in this week.

Construcation of the laser transport line will be started in this week. We intend to finish it in the next week.

2. Vibation measurement of Shintake monitor table was perfomed with Benoit Bolzon (LAPP).

Correlation between the table and the ground is good from 1 Hz to 50 Hz in all direction.

Correlation between QD0 and Shintake monitor table was also measured and it was a little worse in horizontal direction.

Detail and result of the measurement will be presented at ATF2 weekly meeting, maybe on November 12th.