Laser-wire setup at the ATF extraction line

This page describes the setup of the laser-wire to be installed at the ATF extraction line.
The initial part will be installed at the ATF in Autumn 2005.

The system is made of the following components:
Electron Beam diagnostics tools
A photon detector (calorimeter)
A laser
Laser optics
A vacuum vessel
ATF beam control
DAQ and control system
A scanner
An interferometer

Tests to be done at the ATF (without the vacuum vessel)
Preliminary calendar for 2005

Colour code:

Items that are ready or near completion

Items that not yet ready but close from completion or no major work needed

Significant work to be done

Latest changes :

• 14/04/2005: Major update following the March trip to the ATF and the discussions during the April 5th meeting ( talks discussion slides discussion summary ).
• 04/02/2005: Link to a proposed DAQ scheme added.
• 01/02/2005: Items discussed on Jan 28 have been added
  • Laser safety
  • Laser diagnostics and optics
  • APD calibration
• 17/01/2005: Document updated after the ATF planning meeting and the DAQ meeting:
  • Jitter measurements added to the plans for March
• 06/01/2004: This document was updated following the phone meeting with Marc Ross at SLAC.
  
  • The e+ BPMs will be used with the FONT electronics
  • Goals and dates (1-18 March; 2 weeks of Beam: 7-18th of March) of the winter run have been decided
  • Spring run dates: May 23rd to June 3rd 2005
  • A Preliminary calendar of the future tests until the end of the year has been discussed

Electron beam diagnostic tools:

• The ATF_CONTROL system will provide us information on the beam status and a rough idea of the beam position.

  Similar code exists and has been tested (Nicolas)

• We need to decide if we need the e+ BPMs (how many? 1, 2 more?) and with which electronics (Bergoz? FONT?)
  

  BPM already installed

  Need to decide if we need them and with which electronics.

• A wire scanner will be used to measure the electron beam position. This wire-scanner will be located outside the vacuum vessel and will be bolted to it.

  The e+ wire scanner will be available for our tests.

  The wire has been fixed (Gold coated Tungsten 10 micron thickness).

  Need to write the control instructions for the wire (sample code has been provided by Fukuda-san).

Photon detector:
(This device is similar in purpose to the calorimeter used at PETRA)

• A lead photon-converter air cerenkov system will be used to convert high energy photons into showers of visible photons.

  Provided by Hayano-san and tested in October 2004/March 2005.

• An avalanche photo-diode (APD; model: Hamamatsu C5658) could be used as photon detector.

  Provided by Hayano-san and tested in October 2004.

• A PMT (provided by Marc Ross) could also be used (it would give us a bigger signal).

  To be tested in May 2005.

• We may need to calibrate the photon detector later.

  Will not be done in the first phase of the project.

Laser:
Laser specification based on the June 22nd 2004 ATF Laser-wire meeting. .

• 300 mJ per pulse
• M²= 1.25
• Wavelength YAG: 532nm
• Pulse length: 200ps
• Repetition rate: 10 Hz
• Position jitter???

Laser optics

• A strong focusing lens has to be designed in order to demonstrate the feasability at the ATF of a spot-size of the order of 1 micrometer. The specifications of the lens are posted here. We will start with an easier lens (giving us a spot-size of 2 micrometers). We need to check that high power pulse do not affect the refracting index of the glass and thus the performances of the lens.

  Preliminary design reviewed but we need to have a final design and manufacture the lens

• The optimal laser spot-size has to be calculated and will depend on the electron beam parameters.

  Calculations in progress (Nicolas).

• Laser beam delivery optics

  Design proposed by Chafik, to be confirmed in May.

• Beam profiler

  Need to buy a commercial beam profiler and (later) to design one that works at our repetition rate (Stewart). Profiler has been ordered

• Fast photodiodes

  Gary + Stewart

• Energy meters

  Siggi ? + Nicolas

Vacuum vessel:

ATF beam control:
ATF beam parameters:

• Energy: 1.28 GeV
• Bunch length 26 ps
• Population: > 0.5 x 10¹⁰ electron/bunch
• Beam size at IP: to be discussed in May

  A lot of work may need to be done to reach 1 micrometer vertical beam size (SLAC, Leo,...).

DAQ and control system:
The DAQ must gather the information of all other sub-systems to produce a plot of the scan.

• Central DAQ coordination
  

  The code written for PETRA will be re-used as much as possible.

  May be tested only in September.

Scanner:

• We will use a slow scanner as the rep. rate is of the order of a few Hertz
  

  Work in progress (Chafik)

• Learn how to use the laser
  

  Need to learn from the e+ people

• Validate the design of the vacuum vessel and the laser delivery system
  

  Need to agree with KEK

• Study the electron optics and dispersion correction
  

  No optics has been validated yet

Preliminary calendar for 2005 (in reverse order)
Link to the ATF schedules

• 17/12/2005: ATF shutdown, end of Year. Full scan must have been completed
• 12/2005: (2 weeks) Full system installed, attempts to do a full scan.
• 11/2005: (1-2 weeks; 3 weeks available) All Hardware installed. Hardware comissioning and DAQ debugging
• 10/2005: SLAC installs new extraction kickers at the ATF
• end of 9/2005: Install the vacuum vessel + check all individual components in situ. All hardware must have been installed (vacuum vessel and focusing lens brought a luggage).
• 7-8/2005: Vacuum vessel tests in Oxford (6 weeks).
• 20/05/2005 - 04/06/2005: Spring beam run: Check the electron beam optics, measure some compton photons, have the vacuum vessel design approved
• end of 5/2005: Vacuum vessel design must be approved (needs 4 weeks to be built).