I. General Statement of Laser Wire R&D plan

A laser profile monitor was tested at the low energy (750 keV) end of
the BNL linac. This hardware will be installed in the high energy (HEBT,
200MeV) line of the linac during August 2001. The location is in the old
linac-AGS transfer line which is not used for beam transport so we will
have more control over the beam current and pulse length than we had in
the low-energy test.

In the low-energy test no lenses were used between the laser the ion
beam. For the HEBT test the laser beam will be focused by two
cylindrical lenses. A 300mm focal length lens creates a very broad 1mm
waist transverse to the ion beam and a 50 mm lens spreads this line
focus along the ion beam direction to reduce power density on the
graphite beam stop. This combination of lenses has been tested and gives
a line focus 1mm wide and 25 mm long at the beam center and 3mm x 50 mm
at the beam stop.

For the low-energy test the signal detector was a Pearson current
transformer with a permanent dipole magnet to remove the stripped
electrons from the ion beam. In addition to the current transformer we
are installing two single-plane beam position monitors, one in front of
the laser and the other after the transformer. The signals from the two
striplines in each BPM will be combined, one combined signal will be
inverted and the two will be added together. This is to test the
feasibility of using the beam-current signal from BPM\'s as the LPM
detector.

We will investigate the possibility of using difference signals from the
BPMs for halo measurement. The power in the BPM difference signal varies
as the square of the offset. We will also consider the possibility of
adding an electron detector to the beambox at a later date.

The LPM location is 7m downstream from an X-Y wire harp profile monitor.
Between the wire monitor and LPM are two quadrupoles. We will not be
able to compare absolute profiles from these two instruments. However we
will be able to adjust the optics to cause changes in the beam widths.
We will check that relative changes track between the two instruments.
In addition, a carbon wire will be installed in the beambox, permitting
direct comparison of profiles.

This test should be a crude test for laser lifetime in an accelerator
radiation environment. The plan is to place an integrating dosimeter at
the laser to give a lifetime measurement.

II\. Open Issues that will be Addressed:

1.  Experimental S/N for various measurement options

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a.  single BCM or sum signal from BPM

b.  differential BCM or BPM

c.  possibly electron detector (one might even imagine locking in to a
    diode laser if an electron detector were available).

d.  possibly loss monitor, although this option is perhaps less
    desirable than the others because of uncertainty in where losses
    will occur.

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2.  Radiation hardness

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a.  measured effect of accumulated dose

b.  paper study -- tech note will be written, in collaboration with
    partner labs

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3.  Quality of profile measurement - an evaluation will be accomplished,
    based on comparison with harp and wire scanner data.

4.  Halo measurement -- this will be a part of the S/N program mentioned
    above

III\. Personnel

Peter Cameron -- one man month

Roger Connolly -- two man months

Marty Kesselman -- one man month

Bob Sikora -- one man month

John Cupolo -- one man month

AGS will provide motion control at no charge to SNS

IV\. Hardware -- all hardware to accomplish the R&D program is in house.

V. Schedule

1 Sep -- Hardware installation complete, begin profile measurement

15 Sep -- preliminary measurement results available (in time for ASAC)

1 Dec - laser wire PDR

1 Feb -- measurement program complete

VI\. Cost for production units -- direct cost should be between \$7K and
\$10K more per unit than Carbon wire. Some significant amount of EDIA
has been completed for MEBT laser wire, and the process of mounting the
experiment at 200MeV will significantly reduce the amount of EDIA
required. An estimate of an additional \$100K to \$200K for EDIA is
probably reasonable.