Cryogen usage

Approximate cryogen consumption and service frequency for CSO instruments.

• Usage in liters.
• When the Sharc II low temperature stage is not cycled, 15 l of LHe will last 6 days.
• Zspec requires daily LN₂ service.
• Additional LN₂ for receiver tuning, calibrations, etc.: 3–5 l daily.
• LHe supplied in 60 l or 100 l dewars, nominal contents in Hilo.
• Because of depressurization and other losses, LHe dewars arrive at telescope with 80-85% of contents.
• LHe availability on short notice may be difficult.
• LN₂ supplied in 160 l or 180 l tanks.

• This spreadsheet provides an approximate estimate of cryogen costs.
  • Change the number of observing nights (in red) for an approximate scaling.
  • The estimate is reasonable for 3 < nights < 15.
  • Costs are subject to change.
  • Final costs will depend on instrument and cryogen delivery schedules.
  • Assumes a Sharc II cycle every night.
  • The heterodyne instruments include 5 l /day of LN₂ for tuning and calibration.
  • The sidecab receivers are combined.
  • For the sidecab and 850 GHz receivers, 60 l LHe dewars are used.
  • For the other instruments, 100 l LHe dewars are used.
  • LHe dewar quantization is only approximate.
  • LHe boiloff from the delivery dewars is ignored.
  • For the LHe dewars, rental days = observing nights + 2.
  • Staggered deliveries of LHe are ignored.

• Chart/MVE Cryogenic Gases Data Book
• Chart/MVE Cryogenic Gases Data Book (alternate source)