Visit of b.163 - FRESCA

Thursday 18 Jun 2020, 14:00 → 16:00 Europe/Zurich

Dear Sergio,

 

Thank you for the summary.

• As I pointed out in the discussion, a two stage electric heating system (1^st: 100W, 2^nd: 50W) seems ideal if the He flow is sufficiently small. Here is a publication about a system with such a two stage heating system for critical current measurements at variable temperature. https://ieeexplore.ieee.org/document/8263150 It is not the same kind of experiments, but many of the boundary conditions are similar. This is just to show you what can be done with a simple two stage electric heater. In the case of this publication, there was an additional heat input from the current injection into the sample that had to be compensated by the second temperature control loop. In your case that should be even simpler. In this example, the +-0.01K stability could be maintained for hours, even with strongly changing current going through the sample.
• There is also a Lakeshore M224 for 12 channels of TT measurement (Cernox, PT, diode, etc)
• FRESCA should restart operation September / October 2020. I will remain operational till autumn 2021 for the installation of FRESCA2. Commissioning of FRESCA2 is planned for spring 2022. After commissioning of FRESCA2, the main part of the cable measurements will be in FRESCA2 resulting in good FRESCA1 availability.
• This means there will be a lot of cable measurements in FERSCA1 from September / October 2020 to autumn 2021. How many cooldowns and measurement days would you absolutely require during that period?
• There is the possibility that the cryogenic system and the 16kA circuit of FRESCA1 is finished before the 32kA circuit is ready for the cable measurement. This could open test slots in September. This is only hypothetical, we try to finish the RT cables and the control system for the 16 kA circuit first to allow cryogenic commissioning of FRESCA1. With the reduced personal on site and with the limited availability of services at the moment, it is difficult to foresee how it will develop.

Best regards,

Christian

 

From: Sergio Calatroni <Sergio.Calatroni@cern.ch>
Sent: 23 June 2020 10:19
To: Christian Barth <c.barth@cern.ch>
Cc: Torsten Koettig <torsten.koettig@cern.ch>; Florian Elie Rene Girardot <florian.girardot@cern.ch>; Laetitia Dufay-Chanat <laetitia.dufay-chanat@cern.ch>; Luca Dassa <Luca.Dassa@cern.ch>; Kristof Brunner <kristof.brunner@cern.ch>; Agostino Vacca <Agostino.Vacca@cern.ch>; Andrew John Lees <andrew.lees@cern.ch>
Subject: Fresca 1

 

Dear Christian,

 

I’d like to thank you again for the very instructive visit to the FRESCA facility last Thursday.

 

For those involved in the project and who could not take part (in particular Kristof, who has the project on his shoulders for his PhD, and Luca, who is in charge of the design for MME) I write down here a few “bullet points”, as a reminder of what we discussed. Since I did not take written notes, please feel free to modify and complement!

First of all, let me anyhow recall that this is part of what we call “impedance project”, which is an official TE project of which you can find the description here https://edms.cern.ch/document/2002283/1.2

• We are in the phase of designing an insert for FRESCA with the goal of measuring impedance of HL-LHC and in future FCC-hh beam screens. Several novel surface treatments or even the use of HTS are envisaged, which make these measurements necessary, in a temperature range (4.2K)-50 K and in a strong dipole field (9T FRESCA1 -  14T FRESCA2) . We target FRESCA1 for our study, knowing that the insert should be compatible with FRESCA as well.
• We need a temperature regulation and accuracy of +/- 10% at any temperature, which should be kept for ~30 minutes (duration of one measurement cycle). Rationale for this: RF impedance is related to surface resistivity, which in turn has a dependence proportional to temperature. Relative accuracy in temperature -> relative accuracy in the measurement.
• After discussion in our small project team (MME, Cryolab) we are converging on the idea of a phase separator providing cold gas to the bottom of the system. Temperature of the system will then be regulated by regulating the temperature of the gas. A first 3D preliminary  model of the system is attached.
• First test are underway at the Cryolab to understand the needs in terms of flow
• After discussing with you, we are happy to see a strong support from your side. Hardware will be available: Lakeshore temperature controllers 100 / 50 W in power.
• We understand we could rely on your help and support for setting up the control system and data acquisition.
• In general terms, you comfort us in the choice of the cooling principle. Plenty of space is available in a standard FRESCA insert for locating a phase separator (above / below lambda plate, or even without lambda plate which is probably not necessary in our case)
• You also confirmed that the best approach would be to copy/paste as much as possible from existing inserts, knowing that out needs in terms of weight and heat inleak are much smaller than for SC cables (basically, 4 thin RF cables plus connections for a few thermometers and heaters)
• FRESCA is under maintenance / upgrade. There will be an extended time slot spring 2021 – autumn 2021 between end of the upgrade and beginning of commissioning of FRESCA2 which could be well suited for commissioning of our system (please correct/confirm!)
• We have to clarify how much liquid helium flow we need or we can accept (min / max flow) for our purpose. A meeting with Andrew Lees is scheduled for this purpose this afternoon (in copy to this e-mail as well.)
• On this purpose, Luca and Kristof are busy simulating / evaluating the thermal loads.

 

Best regards,

Sergio