P1.5 SW & HW functional checks and cryostat cooldown

• Phase : 1
• Status : COMPLETE
• Category : Unpack, Assemble, and Verification (C1)
• Recurrence : once
• Duration : 1 day

Description

• When the electronics are switched on, verify individual services working and initialize the motors, send to nominal positions, and verify the logging. Cool down the cryostat.

Prerequisites

• SHARK-NIR connected to the LBT network (P1.4 should be completed).
• Electronics on.
• A script to initialize the motors.
• Vacuum Pumping in P1.4 should be complete.

Procedure

• Switch on the electronics cabinets and individual components.
• Start individual services.
• Initialize all motors together (using the buttons in the final SW GUI).
• Check also the button which puts every moving component in its resting position.
• Check in the final version of the SW GUI if the individual initialization buttons work.
• Check if the SW (HW if present and needs to be checked) limit switches are triggered and check the logs.
• Check if the SW part of switching ON and OFF lamps in the calibration unit works.
• Check the electronics/SW of the CRED-2 and ALPAO-DM (& RTC). Make sure that they both can be individually switched on and off remotely.
• Start the SCICAM electronics and acquire (and store) an image in warm conditions.

• Start the cryostat cooling down sequence (see the cryostat manual SHARK-NIR_SO-MAN-001).
• Check how the system performs every 30 minutes.

Templates

• SHARKNIR_gen_init (not released)

Success criteria

• All the services are up and running with no fatal errors and understand the errors or warnings if any.
• All the motors are working, initialized, and sent to the nominal positions.
• CRED-2 and ALPAO-DM electronics and SW working as expected.
• Cryostat cooled down without any issues.
• The temperature at the detector is stable at ~78K.

Notes

• Vacuum Pump details, usage, and LN2 fill/refill: First, we need to pump a guard vacuum on a dewar. This requires a pump capable of pressures below 1 mTorr. Although a diffusion pump is capable of providing a high vacuum, a turbopump would be preferable. A pressure gauge capable of reading below the 1 mTorr range is also essential for determining the extent of high vacuum achieved. When we reach the guard vacuum on the dewar, we need to valve the dewar onto a turbopump. If a turbopump is not available, a diffusion pump is acceptable. If a diffusion pump is used, make sure that the pump's cold trap is filled with liquid nitrogen. Yes, the cryostat shall be pumped off from the day before LN2 refilling, and be on UPS (so if the power goes off the pump is still working, otherwise we risk losing the vacuum in the cryostat). The dewar to the pump interface is a KF-25 vacuum flange. Regarding the LN2, for the first fill, we would require 40L. For every refill in 48 hours, we would require about 15-18L of LN2.
• The cryostat is equipped with a small amount of charcoal getter, which will become effective below 120K. For this reason, it is best to leave the dewar on the pump while filling with nitrogen, and until the charcoal itself has cooled. Since the pump will maintain the vacuum while the charcoal is cooling, the charcoal can then absorb what outgassing occurs once the dewar has been taken off the pump. No getter is required on turbopump. The cryostat has to be vacuum pumped also after its installation at the telescope (still, no getter required).

LBTO support

• Liquid Nitrogen refill is required in the cleanroom. For the first fill, 40L of LN2 is required. For refill, every 48 hours, 15-18L of LN2 is required (see Notes section above for more details).
• Vacuum pump and support for cooling down the cryostat. We do not yet have the dimensions of the vacuum pump (available from LBTO) and how the LN2 refill will take place. If they will be done using long hoses then both the vacuum pump and LN2 tank can stay outside the clean tent (see Notes section above for more details).
• We will require UPS connected to the turbopump when pumping vacuum in the cryostat. UPS which can hold the power for 15 minutes would be sufficient. In case of a power outage, within 15 minutes, one of the SHARK-NIR team members can go to the pump and close the valve preserving the vacuum within the cryostat.

Results

• Shutdown and startup scripts have been tested. Several templates have been tested. All motors are moving as expected.
• We tested the functionality of the LS-180 stage (deployable arm) with Mercury and Mikromove, and all was fine. It was reinserted in Box-3, which can now be stored until the next run.
• We had a couple of minor issues (one with bearing limit switches, which were adjusted, and one with one ADC motor, both solved). We defined new SW limit switches to be included for bearing derotation: [131 deg, 318.5 deg].
• We installed a support flange (removing part of it because of mechanical interference) to hold a technical camera (AVT Alvium 1800 U-2040m (pixel size of 2.74 um) in place of the SCICAM and acquired an image of the PSF, which looks nice. The next step is the scientific analysis of FWHM both broadband and with a narrow (10 nm) 633nm filter.
• Manny, Ken, and the SCICAM will likely come up the summit on Thursday 30th (30-06-2022) afternoon, it will be then vacuumed and cooled down.

Date performed and by whom