Cryogenic platform with vertical suspension:
a practical approach
E. Majorana
(INFN – Rome)
ELiTES 3rd General Meeting
Hongo Campus – Tokyo – 9-10 Feb., 2015
UPDATE OF CRYOGENIC PAYLOAD DESIGN AND PREPARATION OF PROTOTYPE TESTS
(K. YAMAMOTO)
A. Hagiwara
Schematics (T. Sekiguchi, D. Chen):
IM is the main steering body of the mirror. According to the models
IM is affected by two main sources of noise
FROM THE TOP
Vertical TN  Horizontal
Fo~ 0.3 Hz .
Q ~ 200
FROM THE SIDE
Cryogenics tech. noise  possible ancillary passive attenuation at the
level of cryostat shield easy to conceive
 need of further attenuation through PF blades
GAS behavior VS T (H. Hennes et al. FEA and tests with ):
1 dE
E dT
1 dL
a=
L dT
THERMOELASTIC
OF THE BLADES
THERMAL EXPANSION
OF THE PLATE
E. Hennes, ELiTES 2nd General meeting
g=
Ext Inj Bench of AdV (NIKHEF)
FEA VS real case checked  ~ OK
T
VERTICAL POSITION
DRIVEN BY g
FREQUENCY
DRIVEN BY a
WORKING POINT
UNCHANGED
WHAT COULD BE DONE (YESTERDAY) (H. Hennes et al. FEA and tests with ):
Cryogenic KAGRA has to ensure performance at low temperature.
By choosing proper materials one can tune g » 0 , is it really feasible ?
Probably yes, but through an extensive study, for KAGRA cryogenic prototype it seems late
the advantage:
- scalable effect, small facility can be used
criticality:
- 50 grams accuracy in tuning is required, even assuming a perfect result (g » 0)
for a small prototype would it be achievable once the one the real filter 1:1 is built ?
A conservative approach:
Meanwhile the tests on materials go on on small-scale facilities a direct test, using CuBe
can be conducted on 1:1 cryogenic platform
knob
Needed force
Expected m*= 5-10 kg
flange
Motor?
Termometer
E. Hennes,
GWADW 2014
Light rigid shaft
(ex,G10, Vespel®)
Any
position
sensor
RoomT
80 kg
20 K
80 kg
20 K
80 kg
dummy payload
Issues: check thermal isolation from 20 K environment by checking first min operation T of the
Gauge. Check shield pass through versus cryostat design.
Check cooling time issues. ~ 200 kg cooling. In 3 runs we measure it; LN2 cryostat available?
The driller used by Curiosity has a cryogenic load
cell working at low T: commercial suitable
devices do exist but they reach at most 190 K
Care in the experiment design
Given the tight schedule a
commercial product is preferable
Cryogenic KAGRA has to ensure performance at low temperature
Extra –load saturates the mechanical range
Any
position
sensor
Room T, filter saturated, the
suspension is set in position
using the top-stage motor
GAS in range at low
temperature with 10 g accuracy
thanks to the extra-load
20 K
check
80 kg +m*
dummy payload
80 kg +m*
In practice the extra mass can be placed on the keystone or on the GAS (not recommended
in the real installation). If IM is composed by two parts (K. Yamamoto et Al.), the mass should
be placed on the upper one.
It is important to start soon the experiment and platform design because it impacts also on
the IM upper stage design.
Example of practical experiments in the context of ELiTES collaborative effort
Ext flange
exchange gas
/ evacuated
fp = 0.9 Hz
2 wires
clamp
5 kg
Fiber bundle sensor
~ 10Hz
Seismic (VFC)
3 Susp wires
A suitable
design
will
developed
according to:
Firstbe
stage
shield 40K
3 Susp wires
- PT impulse harmonics VS system modes
second stage chamber 8 K
- Check of VFC control BW (fBW< 6-8 Hz max)
- Design of capacitive actuator
Critical issues
Massive block
- Actual recoil losses (to be studied first with
sensor
dummy
dielectric rods)
2 Susp wires
- Control performance stability few-days runs
- Environmental stability
capacitive
actuator
electrode
1st ELiTES meeting Oct. 2012, Tokyo.
E. Majorana
Dan Chen measurement in Rome, 2013, 2014
Ext flange
3 Susp wires
First stage shield 40K
3 Susp wires
second stage chamber 8 K
Massive block
sensor
2 Susp wires