1. Columbia Astrophysics Laboratory
Cryogenics
and
Cryostat Design
Karl-Ludwig Giboni
Columbia Astrophysics Laboratory
XENON1T Meeting
Zuerich, 27 February, 2010

2. Mass Increase by factor 10 – 20, but not simple scale up.
XENON100 : 50 kg fiducial. 170 kg total
XENON1T : 1000kg fiducial, 2400 kg total
Mass Increase by factor 10 – 20, but not simple scale up.
Main reason for changes:
Cryostat :
1. Size
Shield with Water or Liquid Scintillator
Opening to Top
Copper design for lower background
Limited cooling Power
Cryogenics :
1. Limited cooling Power
Filling and Recovery time
Long time storage
Recirculation Rate

3. i.e. servicing detector in situ.
Size
Instead of 170 kg there will be 2.5T filling the cryostat, i.e stronger
support structures needed
Access to interior has to be easier than XENON100, but
pieces to be moved are bulkier and heavier.
Shield with Water or Liquid Scintillator
Early assumption started from passive (Lead-Poly) design
Many ideas not easily applicable to water or L.S. shield
Large water shield might be to high to remove detector from top,
i.e. servicing detector in situ.
Safety issues must be addressed

4. Limited Cooling Power
We will never have 10 PTRs. Maximum 2.
We need spare cooler, i.e. 2 coolers including the spare.
Thinner supporting materials (Copper?, Titanium?)
Better thermal insulation
Cryostat design is not only influenced by shield,
but also by TPC design
However, we should not forget the lessons learned
from XENON10 and XENON100

5. Filling and Recovery Time
For 170 kg we need about 2.5 days, i.e. about 1 month for 2.4 ton,
but limited cooling power.
If we store xenon in liquid form, transfer rate 100 liter(liquid)/hour with
Barber Nichols pump, as in MEG, i.e. fill time < 1 day.
Similar time for recovery in liquid form.
Time to prepare liquid for filling, e..g. Krypton removal, during
experiment set up time.
Long Term Storage
We cannot handle battery of 50 2A cylinders underground.
Concept similar to MEG.
Transfer xenon to liquid dewar for storage.
1000 liter dewar with PTR for cooling. Low thermal losses (< 20 W) Design by Taiyo Nissan Sanso.
Without cooling: Pressure rise over 45 hours is < 1 atm? No additional
emergency storage necessary.

6. MEG Set Up Detector Liquid Storage Tank Purification System
Gas Storage
Tank
We want 2 dewars for off-line xenon circulation for purification and Krypton removal

7. Liquid Storage
Gas Storage
1 Tank
1000 liter
<20 W Thermal Loss
1 PTR
8 Tanks
250 liter each
60 bars
360 kg each

8. Pressure Rise in Liquid Tank with No Cooling
0.9 atm in 44 hours

9. Recirculation Rate Cooling power will be very limited in XENON1T.
During recirculation 1 PTR (200 W)
We have to cover heat losses in detector,
and leave some room for PID regulator.
New tests at Nevis with small system
Small PTR with limited cooling power
(29 W total)
Commercial brazed plate exchanger
All stainless steel, copper brazed
Similar model, but different manufacturer
Used for small PET test system at KEK

10. Flat Plate Model FG3X8-20, GEA PHE Systems
Cooling Power Limit
for PDC08: 29 W
Heat Losses: 12.5 W
Slope: 0.34 W/SLPM
Offset: 2.26 W
Efficiency: 96.6 %

11. Extrapolation to PC150 PTR, i.e. XENON100
Without other limitations the flow rate would be limited to 250 – 300 SLPM.
If these rates are possible, liquid recirculation would be not necessary, and
too difficult
For the cryogenics there is a baseline concept, but this
also still requires some work.
Of course, there might be concepts which are better
suited, but the development time is limited.