KAGRA vibration isolation meeting (8th of August 2012)


Attendees: Sekiguchi, Takahashi, Ishizaki, Uchiyama, Yamamoto

Ryutaro: Pre-isolator experiment. 2mm thickness shims are inserted.
So, finally, the friction between the coil and the magnet disappears.
Ryutaro and Takanori put load on the pre-isolator. Now, the load is 600 kg.
The resonant frequency of the pre-isolator is slightly  higher than 0.2 Hz
(In the
case without load, the resonant frequency is about 1 Hz).
If the 80kg load is added, the pre-isolator is at critical point. Takanori
brought
the lead blocks from the basement lab (they belong to Prof. Kuroda).
Tomorrow, Takanori and Riccardo are going to put the lead blocks on the
pre-isolator ([kagra-vi 00166]).

Schedule of the pre-isolator:
(1)The load is put and the resonant frequency is adjusted.
(2)If the resonant frequency is lower than 80 mHz,
the diagonalize of control system is started. Then, the robust control
system is completed (Riccardo's comment after meeting: maybe one should start 
even at this point, then refine the diagonalization as we go,
 will discuss with Takanori).
(3)The meeting of the Physical Society of Japan (11th of September).
(4)The load is put and the resonant frequency is adjusted. The goal is 30
mHz.

Takanori: Brittleness test of Maraging at low temperature
Takanori, Yusuke Sakakibara, Kazuhiro tried this test this evening.
The maraging was put into liquid nitrogen. Takanori hit it with hammer.
It was NOT broken. Fine.

Simulation with the local damping
Takanori asked Masayuki Nakano (a freshperson of
institute for cosmic ray research) to make the silumation with the local
damping (Riccardo's comment after meeting: we should first add also 
the damping using the shadowmeter using the suspension wire
at the ceiling of the cryostat cavern, that will damp the first pendulum mode 
of the chain, which is expected to be the first offender.).
Takanori expect that the easiest way is the improvement of the Mathematica
code
developed by Takanori.
Will Masayuki join the KAGRA vi mailing list ? We should ask his opinion.

Kazuhiro Agatsuma joins this mailing list.

Kazuhiro: Euler Buckling spring for cryogenic payload
Hideharu visited the institute for cosmic ray research today.
He, Ryutaro, and Kazuhiro discussed the Euler buckling spring.
He confirmed that the requirement of the slenderness ratio, which depends on
the dimensions of the spring. He will make new spring made from BeCu based on
this requirement.
Analysis of the experiment result looks strange. It is an issue
which must be considered again.

Although Euler spring is one of the candidates, the other ones for
the cryogenic payload must be considered
(Riccarco's comment after meeting:what is the use of Euler springs? 
I first proposed them, we briefly discussed them,
then I convinced myself (maybe not you all) that they are not useful for our
purposes, that if we need a cryo spring for the intermediate mass we should stick
with what we know, and we can do just as small and at lower frequency.  Incidentally
the Euler spring is more prone to creep, it did not work until I provided David
Blair with maraging.). Kazuhiro must consider the
roadmap of the
cryogenic payload.
And the schedule of the candidates of the cryongenic spring must be told
to him (Riccardo's comment after meeting: if we need to design GAS springs, 
we can do in no time, we have the know how.).