Testing Crystals at FACET-II: discussion

Wednesday 18 Jul 2018, 14:00 → 15:00 Europe/Zurich

Participants: Laura Bandiera, Andrea Mazzolari, Andrea Latina, Daniel Schulte, Rogelio Tomas, Victor Tikomirov, Uli Wienands

 * Uli remarked how the use of ESTB line, instead of FACET-II itself, would simplify the approval process of a proposal, moreover there is already experience and equipment at ESTB from previous Crystal experiments. We decide to go for ESTB then.

* The one installed at ESTB is a Silicon crystal 60 um thick. This has been used in the past for particle steering with large success, but results related to emission of radiation are incomplete and so they were never published.

* Uli will contact Casten Hast for check the status of the previously used hardware

* Something that could be improved w.r.t. the previous measurements, are the counter at the end of the line. Andrea L, Daniel, and Rogelio will see if CERN can provide a better one. Also a collimator along the beam-line might need improvements. Collimator is now located before the gamma detector. Radiation is generated in the interaction between particles and the collimator, increasing the backgorund.

* Tikomirov will check what parameters should be changed to improve the measurements considering the case of silicon crystals.

* Andrea M gave an estimate of the required time to manufacture crystals: it might require months, depending on the thickness (the thicker, the easier the production process). A crystal with thickness less than 500 um could require about 6  months, a crystal with thickness larger than 500 um about 2-3  months. This timeframe includes time needed to purchasse the prime-material.

* In the context of the CLIC positron source, it would be important to validate the simulations and the estimates of the photon production in the channeling process in a Tungsten target. Typical thicknesses of CLIC positron source's crystal targets are in the range 1.5 mm to 2.2 mm, with impinging electron of 3 GeV energy. We need to find a prototype crystal.

* Uli will contact Casten Hast to check if and how a new target could be installed

* Tikomirov proposed where a Tungsten target could be found.

* Andrea Mazzolari says that in Ferrara we have Tungsten crystals. One of such crystals come from Uggerhoj. We have W crystals also from other sources. The topic needs to be investigated deeply.

* Rogelio asked about the crystals for focusing, and it is realised that this subject requires more R&D work. We decide that for the moment it should be kept aside.

* It is decided that we will devote some technical meetings in September (mainly Tikomirov showing the results of his simulations), then we will try to meet in Ischia for the Crystal workshop to define the last details of the proposal.

* There is no strict deadline for submitting a proposal at ESTB. Uli proposes to aim at doing some measurements before the end of the year.