Cryogenic Setup

This page contains information about the cryogenic setup in the cryolab (H037). So far, it just consists of a nitrogen dewar and an aluminium vessel as inner chamber to contain samples. The motivation is described in this early document by Gijs.

cryo_setup.JPG

The nitrogen dewar

  • dewar from China (datasheet)
  • The dewar has a volume of 100 l.
  • To fill it we have to get liquid nitrogen from AMOLF.

Filling the nitrogen dewar

Marcel Vervoort made an agreement with Michiel Witlox from AMOLF that we can "tap" some LN2 from time to time. He will then receive an invoice from AMOLF.

  1. Ask Tatjana van der Ben at the AMOLF post room by e-mail (inkoop@amolf.nl) whether a certain date is suitable (sometimes their tank is empty).
  2. Usually, we take roughly 55 l with two of the small dewars from H038a (the room with the monster source in the vault). This quantity roughly fills half of the large dewar.
  3. Use the cart from Fred's lab (H039) to transport the small dewars.
  4. Say hi at the AMOLF post room (opposite of the filling station).
  5. Follow the instructions at the filling station.
  6. Write another e-mail to AMOLF (with Marcel in cc) and state how much you took.
Past fillings:
  1. Apr 2011: 50 l (exact date unknown)
  2. Jul 5, 2011: 55 l
  3. Oct 11, 2011: 55 l
  4. Mar 26, 2012: 60 l
  5. May 03, 2012: 30 l
  6. April 04, 2013: 55 l
  7. May 06, 2013: 30 l
  8. Jun 03, 2013: 60 l
There's also an (outdated) document of the filling procedure Gijs made.

Insulating cover of the vessel

cryostat_top.jpg

  • A rod connects an insulating cover plate with two handles to the lid of the inner vessel. This rod has a "butterfly" nut that allows to lower the whole vessel deeper into the cryostat.
  • The cover is insulated by a foam layer of about 3 cm thickness.
  • It is safe to touch the handles without gloves.
  • AVOID touching the rod in the centre of the cover because it is directly attached to the vessel.

Inner vessel - test chamber

cryo_inner_vessel.JPG

  • The lid of the vessel (not a real flange yet) supports three rods that hold the heater stage (bottom) and the sample carrier mesh (in the middle).
  • Circular pieces of 3 cm thick foam close the holes of the lid.
  • Mylar foil is covering the inner wall to decrease heat transfer.
  • The bottom is covered by a 3 cm thick foam disc. This disk is not needed! ( see below in next section)
  • Two (or more) PT100 sensors measure the temperature at the bottom (beneath the foam disc), inside the chamber (optional) and above the sample carrier mesh to indicate the sample temperature.
  • A heating element (25 W or 50 W, both at 1 Ohm) can be used to stabilise the temperature (for example at -100 C). Currently, the 50 W heater is in use.

Operation at cold temperature

  • The chamber has to be flushed with (gaseous) nitrogen to purge moist air. This is to avoid condensation on and resulting damage of the components.
  • Cool down takes roughly 2 hours when the vessel is not in contact with the liquid nitrogen. When it is near or under the liquid level (tunable by the "butterfly" nut on the rod above the handles of the vessel cover), this is much faster.
  • The minimum reachable temperatures are around -135 C (vessel at top position) and around -150 C (vessel immersed), respectively.
  • For an example of a cooldown curve see this file: The inner chamber was equipped with thermal insulation (Mylar foil and foam disc) and contained the heater on its platform and the sample support mesh. The heater was turned off.
  • This file shows the temperature curve of cooling down and warming up the chamber suspended over the liquid nitrogen. The temperature control with the 50 W heating element shows good performance. The temperatures inside the chamber were measured in two positions:
    • at the bottom below a insulating foam disc (3 cm)
    • between the sample carrier mesh and the top flange
  • The power supply for the heating element is set to 6.4 V and 6 A, thus roughly 38.8 W. This power is sufficient to keep the chamber temperature stable inside the dewar, but also to heat up the chamber to 95 C ( rather not more, because then the cable insulation starts to melt and this doesn't improve the atmosphere inside the chamber).
  • The 3 cm foam disk at the chamber's bottom is not necessary! There's still a sufficient temperature gradient inside the chamber to avoid too abrupt cooling of samples. Furthermore this reduces the amount of trapped (moist) air in the chamber (that is difficult to flush)!

Datasheets of the glues we use in cryogenic environment

Measurement results

Cold and cryogenic tests of single components

  • Gijs conducted tests of single components during his master project. These are his results.
  • Mechanical/thermal stress test of 4 GridPix detectors (w/o readout) with gradual cooldown down to -130 C. A report of this can be found here.

Threshold scan of Timepix chips at low temperatures

to be filled in soon

-- RolfS - 2013-06-03

Topic attachments
I Attachment Action Size Date Who Comment
Unknown file formatods 111013_cool_down_vessel_wo_heater.ods manage 17.9 K 2011-11-23 - 13:33 UnknownUser Cooldown curve w/o heater
Microsoft Excel Spreadsheetxls 120328_cooldown_w_heater.xls manage 27.0 K 2012-04-02 - 07:36 UnknownUser Cooldown curve w/ heater
PDFpdf 9001-e-v35-Globtop_to_reinforce_the_grid_on_dykes.pdf manage 50.9 K 2012-02-22 - 12:27 UnknownUser Datasheet for the Globtop to reinforce the edges of the grid
Unknown file formatPDF EE129-4-glue_chip_on_pcb.PDF manage 84.9 K 2012-02-22 - 12:30 UnknownUser Datasheet for the glue used to glue chip on PCB
PDFpdf LN2_Dewar.pdf manage 4129.6 K 2012-02-22 - 12:31 UnknownUser Datasheet of the dewar
PDFpdf ara2011-for_PCB-Kapton_guard.pdf manage 178.3 K 2012-02-22 - 12:28 UnknownUser Datasheet for Araldite2011 to glue PCB and Kapton foil guard
PDFpdf ara2012-for_PCB-PCB.pdf manage 153.2 K 2012-02-22 - 12:29 UnknownUser Datasheet for Araldite2012 to glue PCBs together
Unknown file formatJPG cryo_inner_vessel.JPG manage 295.2 K 2011-11-23 - 11:58 UnknownUser Inner vessel of cryogenic setup
Unknown file formatJPG cryo_setup.JPG manage 1690.6 K 2012-02-13 - 13:53 UnknownUser The whole setup incl. the liquid nitrogen dewar.
JPEGjpg cryostat_top.jpg manage 87.8 K 2011-11-23 - 13:15 UnknownUser Top of the cryostat with insulating cover with handles
PDFpdf main_dewar.pdf manage 1222.4 K 2012-02-22 - 12:38 UnknownUser How to use the dewar (plans by Gijs)
PDFpdf main_refill.pdf manage 67.4 K 2012-02-22 - 12:39 UnknownUser How to refill the dewar (by Gijs)
PDFpdf main_tests.pdf manage 19811.5 K 2012-02-22 - 12:40 UnknownUser Results of first cold tests (by Gijs)
Topic revision: r15 - 2013-06-03 - rolfs_40nikhef_2enl
 
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