Minutes from Damage Studies Meeting 20/02/2007

Attendees:

Luis Fernandez, Nigel Watson, Justin Greenhalgh, George Ellwood

During the meeting the following plan was created:

Two stage plan, the first stage demonstrates how to place a sample, move the sample, check for radiation levels and look for microscopic damage after the beam test. The second stage is to look at measuring surface displacement & velocity using either a VISAR or Laser Doppler Vibrometer (LDV).

Assuming that we can use the 4 axis mover owned by Royal Holloway and already at KEK and vacuum vessel owned by KEK. Grahame Blair agrees that we can borrow the 4-axis
vacuum mover for the damage tests, assuming it fits in with their scheduled use for laserwire tests. Borrow wire scanner from KEK but pay ~£10k for consumables. The wire scanner will be used primarily to measure beam size rather than position.

1^st Stage

Use simple sample geometry, probably a cube. Shown figure1. Drill a reference pin hole in one corner; create two channels that are almost through thickness that lead to the pin hole. Use a low intensity beam to scan across x until the vertical channel is found, check this against a downstream BPM, then scan in y until the reference hole is found. Once the reference position has been found, move the sample with the 4 axis mover a known amount in each direction. Then increase the beam power to a point that should damage the surface by melting. Then scan across in a grid pattern trying to damage the surface. After the test check the sample under a microscope for damage.

Figure 1: Beam view of sample

2^nd Stage

Once we are competent in placing and moving the sample try to measure the surface velocity or displacement using either a VISAR or LDV. Use these measurements to calibrate models for stress. Try to damage the sample by creating shockwaves within the material rather than melting as in the 1^st stage.

Actions:

Luis:

Model different beam sizes from 1x30µm up to 7x70µm.

Check photon fluence and total equivalent dose.

Nigel:

Speak to Stewart Boogert who will liaise with KEK people and discuss plans.

Speak to Royal Holloway regarding borrowing their equipment.

Check the procedure for submitting a request to KEK.

George:

Compare lists created by George and Justin and responses from Nigel and put in one document.

Speak to Chris Densham about the differences between VISAR and LDV.

Ask Wilfinger for more information on the graphs he has presented on surface velocities measured with an LDV.

Additional Information

Nigel’s Logbook which records some of the discussion with Stewart Boogert scan1, scan 2

Next meeting

16:00 on Tuesday 6^th March 2007, conference call initiated from RAL.