73rd ATF2 meeting

February 20 14:30- 16:30, ATF LC meeting room at KEK.

1. Emittance growth and correction in ATF extraction line, P.Bambade (LAL)

file , pdf (13 pages, 1.2MB)

Analysis status with MAD-tracking and plans for shifts in coming weeks( (9) -10-11) were presented. You can see the above file with clear explanations.

In the future, we probably will want to see whether OTR measurements could be generalised for faster and more reliable transverse phase space measurements, through estimations at successive points in the diagnostic section of ATF2, complementary to laser-wire and wire-scanner measurements, for emittance evaluation and control. As you know, especially the sigma_13 correlation is very hard to get from wire-scanners (or laser-wires), as it is obtained from a difference of large numbers.

C : A documentation of OTR was uploaded in the ATF-web site. After log-in the http://atf.kek.jp/, go to Library - Others - User upload area - common area, where you see the file entitled "OTR operating instructions.pdf" which has been sent by SLAC colleague.
Q : We may need to check this result with SAD-calculation.
A : There have been many consistency checks between MAD and SAD by M.Woodley.
Q : Naive question to page 5; Are the two results of emittance and beam size consistent, since I naively expect similar function of offset in both cases ?
A :The comparisons in slide 5 were made recently by Maria, using the multipole expansion based for the moment on Cherrill Spencer's field map.
  1. Before QM7 there should have no effects for neither beam size or emittance.
  2. After QM7 one gets as expected an increase of effective vertical emittance from the skew quadrupole focusing term dBx/dx which you have in QM7 once delta_x = 2.25 cm and delta_y is non-zero (about a few mm). For the beam size there is no effect visible yet because QM7 is very short (7.8 cm, almost a thin lens...) and since the local effect of a quadrupole is always to change the beam angular spread, not to change the beam size.
  3. After the septum where the OTR is located, the increase in beam angular spread from the skew quadrupole focusing term dBx/dx in QM7 translates into an increase in beam size. You can see from the point with zero vertical offset that the beam size after the septum is in fact rather dominated by the (natural) angular spread of the beam in QM7. So this shows that the drift space between the exit of QM7 and the OTR location is enough to enable forming onto the OTR more or less an image of the angular spread at the exit of QM7. The increase in effective emittance from cross-place coupling should be computed as the increase in the product of angular spread and beam size (neglecting y-y'correlations for a rough estimation), not from sig_y = sqrt(beta_y * eps_y) which assumes phase-space conservation in the y-y' plane. Hence, looking at the two blue curves, beyond some threshold effect from additions in quadrature and / or y-y' correlations, you can see that they follow each other well: going from 0.4 to 1.1 mm initial offset, you get as you should about a factor 2 increase in both effective vertical emittance and vertical beam size.
, where the last Q&A were exchange with e-mails after the meeting.

2. QBPM installation at ATF2 tunnel, Y. Honda (KEK)

file , pdf (2 pages, 7.7MB)

QBPMs were installed in half of Q-magnets at the ATF2 beam line, i.e. 11 magnets. Also, a downmix (electronics) box was set at one magnet. QBPM and the box were connected with cables, where a 20dB attenuator will be inserted between the hybrid-circuit (combiner) and the box for the commissioning; i.e. 1um resolution with 5mm dynamic range while 0.1um with 500um range without the 20dB attenuator.

3. QBPM System Installation, D. McCormick (KEK)

file , pdf (15 pages, 1MB)

Unfortunately he was absent, but the file shows clear description.

After the meeting, following Q&As were exchanged with emails.

Q : We could not find standoffs for the downmix box in page 7 as Honda-san pointed out in his presentation.
A : As for the standoffs, I have them here at SLAC along with the DC and IF cables. I need to see how soon there will be money to send them to KEK.
Q : What is your plan of the Nanobpm R&D for 2008 - 2010 ? - If the R&D is completed, we could use some of the Nanobpm equipments as you pointed out.
A : I don't know what the program is for the nanobpm. There was idea floating around that the nanobpm system could become a testbed for RF BPM development. At one point I though Urakawa-san said that the nanobpm would have to be shipped back to SLAC for some time due to customs requirements. As for using the VME crate and CPU there might be a speed problem. Reading out 9 SIS digitizers might take too long with the nanobpm CPU.
Q : What is present status of the data acquisition software ( page 15)? - Did you test the software at the test system which has been installed at the ATF extraction line ?
A : The software is the most important issue. From what I understand Stewart Boogert has had a number of routines written that can take data from the SIS modules and do some processing but I don't know how hard it will be to turn those routines in to a EPICS based BPM display system. Justin May has now left SLAC and it is going to be difficult to find someone to write the EPICS software. I think we need to hear from Stewart about the acquisition routines he has and see how hard it will be to turn them into a working BPM control system.
There are further questions;
Q : The following items are listed as "to buy or to be designed". Does it mean KEK has to buy or SLAC is going to buy ?
Q : About the installation work, who is expected to do the actual work? Does it has to be done by KEK staffs (with help of e-cube) with instructions written by Doug-san?
Q : Do you have plan for April-May beam operation? This is the last chance to check the system with beam. I think we should complete the testbed BPM as full system including online software.

KEK site meeting

4. Concrete shields, beam dump and Shintake monitor support

5 shielding block have been sent to KEK from the company, today. All the shield blocks and beam dump will be installed in this March.

The Shintake monitor support will arrive in morning, 12th March, Wednesday, and the complete survey will be done at the company in 7th March by T.Kume .

The laser system for Shintake monitor will be sent to KEK from Tokyo university. The date is not decided yet.