72nd ATF2 meeting

1. Installation of the MONALISA CSM at ATF2, Paul Coe (Oxford univ.)

The monalisa system is based on a laser interferometry of FFI (Fixed Frequency Interferometry) and FSI (Frequency Scanning Interferometry) which measures displacement and distance with respect to fixed wavelength (780nm) and fixed reference-length, respectively. A key system is a distance meter interferometer shown in page 7. Basic performances have been demonstrated with Michelson's interferometers at Oxford university. The FSI resolution has been obtained to be &sigma=70nm in air . The FFI recent results show 5nm RMS in air .

Future plan is (1) to evacuate interferometers improving resolutions, (2) to stabilize frequency of a reference laser, i.e. 20kHz stability for 1nm over distances of 10m, (3) to increase test range up to 10m OPD and (4) to report in several papers.

Paul Coe and Matthew Warden (graduate student) visit ATF using opportunity of participating in IWAA08, KEK. The ATF2 area was inspected and they have detailed discussion on the structure, laser hut location, schedule etc. with KEK colleagues . ( The laser hut width must be less than 2m. )

Laser system for ATF2-Monalisa has been purchased and the optics will be setup in this March. The mounting structure will be constructed in this summer. The whole system could be sent to KEK by end of 2008.

Q : Is the 100Hz limit because of the readout?

A : No. The readout can be 1kHz with enough resolution. The readout frequency was optimized by cost-performance. So, if necessary, higher readout frequency can be possible.

Q : What is the status of electronics for ATF2?

A : 95% of the electronics system have been completed .

C : You could make holes on the top of QD0 as in drawing which you have sent to us (C.Spencer) at SLAC.

Q : How do you dismount such large structure which you proposed in page 22 ?

A : Since we may not pass through a space in the north wall side, the side supports have to be quickly dismounted, say for 10 -15 min. We will investigate this method ( by engineers at Oxford univ.).

C : Such large structure has been proposed as shown in PDF, where the south side was too large.

C : If the pass-way is required, the structure has to be smaller as shown in page 20. In this case, more beams must be added in the structure for higher eigen resonant frequency. Addition of beams and cross-bars could increase it to 80Hz.

Q : After the dismantle, do we need realignment of laser-optics ?

A : We expect that the dismantle effect will be small within tolerance but fine-tuning for interferometer.

Q : We would like to have 3D-CAD drawings in order to inspect possible conflict with QD0, Shintake monitor, alignment tools etc. .

A : LAPP colleagues can provide the FD system, where the sextupole magnets may be simplified. It will take a few months to fully develop the 3D model ( A.Jeremie).

Q : How much is the size of vacuum pipe above magnets and Shintake monitor?

A : The diameter is about 6 inches.

Q : Is it round ?

A : Yes for simplicity. If necessary, the shape can be ellipse of 3in x 6in. The size is necessary for the CSM ( Compact Straightness Monitor of 6D position measurement) which has been shown in the 5th Project meeting by D.Urner ( PDF).

KEK site meeting

2. Status of Shintake monitor support system, T.Kume

We continued to discuss on the support system and the alignment method. Also, we prepared agenda at discussion with the company.

3. Concrete shield status, N.Terunuma and S. Araki

N.Terunuma and S. Araki recently have visited to the company in order to inspect the product. Many photographs taken at the company were shown. The production accuracy was required to +0 and -5 mm, which was confirmed .

Beam dump will start the production in next week, and will be installed in March.