1. Institute for Cosmic Ray Research The University of Tokyo
KAGRA external review
(Cryogenic payload)
Kazuhiro Yamamoto
Institute for Cosmic Ray Research
The University of Tokyo
I will explain the second half of the cryogenics, cryogenic payload.
　18 April 2012

2. I explain the cryogenic payload.
This is a part of cryogenics, but it is also related with vibration isolation system.
There are some minor corrections in document.
I would like to summarize the cryogenic payload. This is a part of cryogenics, but it is also related with vibration isolation system. And, sorry, but, there are some minor corrections in document. If you find the difference between the document and slides, the items in slides are correct.

3. 1. Overview 1.1 Definition of cryogenic payload
System to suspend the cooled mirrors
It is suspended
from vibration isolation system (Type-A)
and surrounded by thermal radiation shields.
Border between vibration isolation and cryogenics.
Other items in cryostat (e.g. baffles)
are also considered.
The cryogenic payload means the suspension systems for the cooled mirrors of the main Fabry-Perot cavity. It is suspended from the vibration isolation system called Type-A and surrounded by the radiation shield. The cryogenic payload is on the border between the vibration isolation and cryogenics. Other items which are in the radiation shield (for example, the baffle to prevent from the propagation of the scattered light) are also included in the cryogenic payload.

4. 1. Overview 1.2 Important interface Cryogenic : Heat link and cryostat
Vibration isolation : Type-A
(development, installation, commissioning)
Mirror : How to suspend mirror,
Coating mechanical loss, Clean room
Facility : Clean room
Main interferometer : Control of payload
Digital systems and Electronics : Control
Auxiliary Optical Systems :
Baffle for scattering light and monitors
As the explanation in the previous sub section, the cryogenic payload is on the border between the vibration isolation (Type-A; development, installation, commissioning) and cryogenics (heat links and cryocoolers). Therefore, the interfaces with these subgroups are extremely important.
The sapphire mirrors are provided by the mirror subgroup. Our subgroup should discuss how to suspend the sapphire mirrors using the sapphire fibers. The measurement of the coating mechanical loss is also managed by the both groups. The clean room should be discussed by the subgroups of the mirror, facility, and ours.
The control and monitor of the positions and angles of the mirrors and payloads are an important issue. Our subgroup considers it in cooperation with the subgroups of Main Interferometer (scheme of the interferometer control) and Digital Control and Electronics (control and monitor).
Auxiliary Optics and our subgroups design the baffle in the cryostat for the (large angle) scattered light by the sapphire mirror and other monitors.

5. 1. Overview
1.3 Design phase
Cryogenic payload is not necessary in i-KAGRA
(room temperature interferometer).
However, the development should be
in progress for b-KAGRA in i-KAGRA phase.
Some cryogenic payload will
be installed in i-KAGRA phase.
In iKAGRA phase, no cryogenic payload is necessary because the room temperature interferometer will be constructed in this phase. Therefore, all items in cryogenic payload are for bKAGRA, not iKAGRA. Nevertheless, there should be progress in the iKAGRA phase because it takes time for development and so on. Some cryogenic payload will be installed in iKAGRA phase (before the observation of iKAGRA).

6. 2. i-KAGRA Cryogenic payload is not necessary in i-KAGRA
(room temperature interferometer).
Nothing for i-KAGRA
Since the room temperature interferometer will be constructed in iKAGRA phase, nothing is mentioned here.

7. 3. b-KAGRA 3.1 Requirement (a) Installation in safe and clean
within the short period
(b) The temperature of the mirror
should be below about 20 K
(with about 1 W heat load).
Inital cooling time shoud be short (1 month).
(c) Control (and damping) of the position
and angle of mirrors at cryogenic temperature
(d) The sensitivity (10 Hz Hz) is not limited
by the thermal noise, external vibration noise,
and control noise.
The cryogenic payload should be installed in safe and clean environment within the short period. The procedure should be considered and investigated carefully.
The sapphire mirrors should be enough cooled. The mirror temperature should be below 20 K with heat load by the light absorption in the mirrors (about 1 W). The initial cooling time must be as short as one month.
The control (and damping) for the angle and position of the mirrors and the other masses are necessary and they must work well at cryogenic temperature.
The thermal noise, the external vibration, and control noise are should be smaller than the sensitivity of bKAGRA.

8. 3. b-KAGRA 3.2 Preliminary design Type-A and Cryogeni payload
14m in height
Vibration
Isolation
(Type-A)
Here, I would like to show the preliminary design. This is the cross section of the tunnel and shaft for the vibration isolation system. It is the vibration system called Type-A. Its height is 14 m. It will be explained by Ryutaro Takahashi on this afternoon. The cryogenic payload is suspended from Type-A, this part and it is in the cryostat. The cryostat is the part surrounded by the black line.
Cryostat
Cryogenic mirror 8 8

9. 3. b-KAGRA 3.2 Preliminary design Cryogenic payload Shield (8K)
It is a schematic view of the cryogenic payload. It is a triple pendulum and enclosed by the radiation shield. The mirror is at the bottom of the cryogenic payload. There are heat links between the radiation shield and the cryogenic payload. Heat generated in the mirror goes along the sapphire fibers which suspend the mirror and heat links and to the radiation shield. This shield is cooled by four pulse tube cryocoolers as this figure.
Sapphire fiber
Sapphire mirror
(20K) 9 9 9

10. 3. b-KAGRA 3.2 Preliminary design Preliminary. 10 10 10
They are outlines of the cryogenic payload. This figure is the view from the laser beam. This figure is the view from the other horizontal direction.
The mirror (23~kg) and recoil mass (about 30~kg) are suspended from the intermediate mass (about 60~kg). The distance between the centers of mirror and the intermediate mass is 30~cm. The intermediate mass and its recoil mass (about 60~kg) are suspended from the platform (about 120~kg). The distance between the centers of the intermediate mass and platform is 40~cm. So, in total, the weight of this payload is 300 kg. 10 10 10

11. 3. b-KAGRA 3.2 Preliminary design
Initial cooling time (by Y. Sakakibara)
Yusuke Sakakibara calculated the initial cooling time. The horizontal axis is the time from the start of the operation of cryocoolers. The vertical axis the temperature. This black line is the radiation shield. This red line is the mirror. It takes about one month to cool the cryogenic payload. 11 11 11

12. 3. b-KAGRA 3.2 Preliminary design
Mirror temperature (by Y. Sakakibara)
Yusuke Sakakibara also calculated the initial cooling time. The horizontal axis is the heat load on the mirror. The vertical axis is the temperature. The red line is the mirror. If the heat load on the mirror is 1 W, temperature is about 23 K. Of course, smaller heat load is better. 12 12 12

13. 3. b-KAGRA 3.2 Preliminary design We continue study ...
External vibration (by T. Sekiguchi)
Takanori Sekiguchi calculated the mirror fluctuation by the external vibration. According to his calculation, below about 1 Hz, the external vibration via heat link is larger than the seismic motion via Type-A. The horizontal and vertical axes are frequency and linear spectral density. This red line is the mirror fluctuation by external vibration. This purple line is the sensitivity of KAGRA. So, the external vibration is enough small. But, this is just calculation and there are some optimistic assumption. So, we should continue the study.
(Vibration via heat link) > (Seismic motion) (> 1Hz) 13 13 13

14. 3. b-KAGRA 3.2 Preliminary design
Baffle for the (large angle) scattered light
The scattered light is one of the serious issues of the detector. In the case of KAGRA, the baffle for the large angle scattered light on the mirror surface will be installed in the cryostat. This is the design by Mike Smith, who is the specialist in the LIGO. The diameter of this hole is slightly larger that of the mirror. The weight is about 10 kg. According to Mike, it should be suspended.
Design from Mike Smith – Caltech
(support from LIGO and U.S. National Science Foundation )
Needs suspension inside radiation shield ! 14 14 14

15. 3. b-KAGRA 3.2 Preliminary design What should we do in near future ?
(1) How to assemble
Details of construction in clean room ….
(2) Control and damping system
to reduce fluctuation and instability
Actuators (what and where),
resonant mode (frequency and Q)
and so on
(3) Noise : Thermal noise, external vibration noise,
noise of control and damping system…
(4) How to suspend baffle for scattered light
In fact, there are some items which we should investigate in near future. Of course, we must consider how to assemble the payload in clean room, and control and damping system to reduce fluctuation and instability. For the control and damping system, the kinds and position of the actuator should be studied based on the resonant modes of the payload. Some kinds of noise, for example, the thermal noise and noise by the control and damping system are also evaluated. And, baffle in cryostat for the scattered light must be suspended. Mike evaluated the noise by scattered light and it is not so serious. However, he pointed out that the resonant peak of baffle itself might appear above the floor sensitivity. 15 15 15

16. 3. b-KAGRA 3.3 Schedule Cryogenic payload must be prepared
in i-KAGRA phase (by Jun. 2015).
In i-KAGRA phase
(a) We propose experiment of 1/4 cryostat
in ICRR (Kashiwa) to check payload perfomance.
1/4 means number of cryocooler, not size.
(b) Other R&D (sapphire fibers ...)
After these investigations, cryogenic payloads
will be procured and installed.
In iKAGRA phase, our subgroup will prepare the actual cryogenic payload to install in Kamioka mine. Therefore, we should check the cryogenic payload performance before the installation, I mean i-KAGRA phase, actually, by June of Moreover, some components of cryogenic payload also must be investigated.
In order to check the cryogenic payload performance, we propose the 1/4 (quarter) cryocooler in the second research complex of Kashiwa campus, the University of Tokyo. Quarter implies that number of the cryocooler is quarter of the actual one (4 cryocoolers), not the size of the cryostat.
Some components of the cryogenic payload, for example, sapphire fibers to suspend the sapphire mirrors, should be investigated.
After these experiments, we will procure and install the four cryogenic payloads. 16 16 16

17. 3. b-KAGRA 3.3 Schedule (which we proposed)
Mar : 1/4 cryostat will arrive at Kashiwa.
Apr Sep : Experiment of 1/4 prototype
Apr May 2013 : Vacuum test and cooling test without payload
Assembling payload
Jun : Installation of payload, cooling test
Jul Sep : Cooling test, damping and control test
- Sep : R&D items (sapphire fibers ...)
Sep : Final design for payload
Jul Mar : Procurement
This is the outline of the timeline. On March of 2013, quarter cryostat will arrive at Kashiwa and the experiment starts. In first two months, the vacuum and cooling test will be done and payload will be assembled. After these test, the payload will be installed and the test starts. We should proceed with investigation for some R&D items, for example, sapphire fibers. These investigation is continued until September of On this month, the final design will be fixed. From July of 2014 and March of 2015, we will procure the payload.

18. 3. b-KAGRA 3.3 Schedule Jun. 2015 - Sep. 2016
Type-A (including cryogenic payload)
Installation and commissioning for end mirrors
Nov Dec. 2016
Installation and commissioning for front mirrors
From June of 2015 to September of 2016, the payloads for end mirrors are installed and commissioned. The same procedure for the front mirrors are repeated from November of 2015 to December of 2016.

19. 3. b-KAGRA 3.4 Prototype test
(1) 1/4 cryostat in Kashiwa (Apr Sep. 2014)
　　　(a) How to assemble and install
(b) Cooling test (initial cooling
and mirror temperature)
(c) Control and damping system
(including parametric instability)
This is indispensable experiment to avoid
many and serious troubles in installation
and comissioning in tunnel (Jun ).
Here I will introduce the proto type test. In order to check the cryogenic payload performance, we propose the 1/4 (quarter) cryocooler in the second research complex of Kashiwa campus, the University of Tokyo. It will be used from April of 2013 to September of In this experiment, we can check and confirm how to assemble and install, the cooling time (initial cooling time and mirror temperature), the control and damping systems, including parametric instability. They are the basic performance of cryogenic payload. So, this is an indispensable experiment to avoid many and serious troubles in installation and comissioning in tunnel from June of 2015.

20. 3. b-KAGRA 3.4 Prototype test
(1) 1/4 cryostat in Kashiwa (Apr Sep. 2014)
　　　(a) How to assemble and install
(b) Cooling test (initial cooling
and mirror temperature)
(c) Control and damping system
(including parametric instability)
1/4 cryostat and its payload are not same
as those of KAGRA.
Number of cryocooler (not 4, but 1)
Mirror and fibers are not sapphire.
Although the ¼ cryostat and payload are similar to those of bKAGRA , they are not the same. For example, the number of cryocooler is one not four as KAGRA. The mirror and its fibers are not be made from sapphire. We should take these difference into account.

21. 3. b-KAGRA 3.4 Prototype test Kashiwa.
Cryocooler for 1/4 cryostat has already arrived at
Kashiwa.
The cryocooler for ¼ cryostat experiment has already arrived at Kashiwa.

22. 3. b-KAGRA 3.4 Prototype test Design of 1/4 cryostat is in progress.
Preliminary.
And, the design of ¼ cryostat is in progress. This is a preliminary drawing. 22

23. 3. b-KAGRA 3.4 Prototype test (2) Some R&D items
(a)Sapphire fibers to suspend mirror
(b)Vertical spring in cryostat
(c)Material for mass and wire
(except for the mirrors and fibers to suspend mirror)
(d)Development and test
of sensors, actuators, motors in cryostat
(e) Thermal noise (Calculation, Q measurement
of wires and coating and so on)
(f) External vibration noise
(seimic motion, vibration of shield,
transfer function of payload and heat link)
(g) Baffles for scattered light
And there are many items for R&D. First of all we must develop the sapphire fibers to suspend mirror. For vertical vibration isolation, we need the vertical spring in cryostat. Material for mass and wire, except for the mirrors and fibers to suspend mirror should be selected. For control and damping, sensors, actuators and motors in cryostat are needed. There are some items for thermal noise; calculation and Q values measurement of wires and reflective coating. We must consider the external vibration noise. And baffles for scattered light must be taken into account.

24. 3. b-KAGRA 3.4 Prototype test
Sapphire fibers to suspend sapphire mirrors
Sapphire fibers to suspend sapphire mirrors is one of the most serious problem. Now we would like to made sapphire fiber with thick end as this figure.

25. 3. b-KAGRA 3.4 Prototype test Test sample (T. Uchiyama)
Sapphire fibers to suspend sapphire mirrors
Takashi Uchiyama draw such figure and looked for the company which can provide the sapphire fiber whose shape is as this figure.
Test sample
(T. Uchiyama) 25

26. 3. b-KAGRA 3.4 Prototype test
Sapphire fibers to suspend sapphire mirrors
Sapphire fibers from MolTech GmbH (Germany)
MolTech GmbH, which is the German company, said yes. And they made 4 fibers and sent to us. This is the photo. I would like to mention that their length and diameter are almost same as what we need in bKAGRA. However ,we should check the quality.
Length = 350 mm diameter = 1.8 mm
Almost as needed in b-KAGRA.
Need to check the quality. 26 26 26

27. 3. b-KAGRA 3.5 Quality assuarance
Before procurement : We should check in experiment
of 1/4 cryostat and the other R&D items.
After procurement : We should check the parts in Kashiwa,
KEK (Tsukuba) or Kamioka site.
Test of sapphire fibers
We pick up some fibers for test
(thermal conductivity, mechanical Q-value, strength).
The other fibers are installed in cryogenic payload.
First of all, we should confirm the items in 1/4 cryostat and the other R\&D. Before procurement, the parts in cryostat should be tested in 1/4 cryostat and so on.
After procurement, if possible, we check parts in Kashiwa (or KEK (Tsukuba) or Kamioka site). Especially, the test of the sapphire fibers is important. Since we cannot use the sapphire fibers which we test, we pick up some fibers for test (thermal conductivity, mechanical Q value, strength) and the remains are installed in cryostat in Kamioka mine.

28. 3. b-KAGRA 3.6 Installation scenario
Jun Sep : X-End mirror
Jun Jul : Type-A installation
Jul Dec. 2015:
Cryogenic payload installation
and test with fixed Type-A
Jan Jul : Type-A (free)
+ Cryogenic payload test
Jul Sep : Mirror is replaced
by sapphire one.
OK, let us start the discussion about installation scenario. From June of 2015 to September of 2016, Type A system and payload for X-End mirror is installed. In this installation, the first priority is the check of the performance of payload. Therefore, at first, cryogenic payload will be test with the fixed TypeA. Next, we check the performance with released Type-A. Until this stage, the mirror is dummy. After that, the mirror is replace by the sapphire mirror.

29. 3. b-KAGRA 3.6 Installation scenario
Jul Sep : Y-end mirror
Jul Aug : Type-A installation
Aug Feb : Type-A test
with dummy load
Feb Jul : Cryogenic payload
installation and test　
Jul Sep : Mirror is replaced
by sapphire one.
Almost same time, I mean from July of 2015 to September of 2016, Type A system and payload for Y-End mirror is installed. In this installation, the first priority is the check of the performance of Type-A vibration isolation system without payload, but with dummy load. After this test, cryogenic payload will be installed and tested. After that, the mirror is replace by the sapphire mirror.

30. 3. b-KAGRA 3.6 Installation scenario
　Nov Dec : Front mirrors
Nov May 2016 : Type-A installation
and commissioning
(Jun Aug : Dual Recycling
Michelson Interferometer (DRMI) experiment
at room temperature)
Sep Dec : Cryogenic payload
installation and commissioning
After we install Type A systems and payloads for the end mirrors, I mean from November of 2015 to December of 2016, Type A systems and payloads for front mirrors are installed. From November of 2015 to May of 2016, Type-A vibration isolation systems are installed. After that, dual recycling Michelson interferometer experiment at room temperature will be done. After that, form September 2016 to December of 2016, cryogenic payloads are installed.

31. 3. b-KAGRA 3.7 Risk management No budget, no cryogenic payload
Budget after March of 2013 (P=3, S=3, R=9)
No budget, no cryogenic payload
Delay of budget may change schedule and
make process of development complicate.
We must win budget !
Here is the risk management. The most serious risk, the risk factor is 9, the budget after March of 2013 because the procurement of cryogenic payload is based on it. Of course, if there is no budget, no cryogenic payload. And, delay of budget may change schedule and make process of development complicate. We must win budget.

32. 3. b-KAGRA 3.7 Risk management (a) Human resources (P=2, S=3, R=6) :
Appendix C
(b) Clean room for mirrors, payload, cryostat,
and vibration isolation (P=3, S=2, R=6)
We (or new associate professor of ICRR ?)
should prepare clean room.
(c) Sapphire fibers (P= 2, S=3, R= 6)
Invesitgation and human resources
(or silicon ???)
The second most serious risks, the risk factor is 6, are as follows. One of them is the human resource. It will be explained in Appendix C. We need careful consideration for the clean room. We hope that new associate professor of ICRR will strongly proceed. The sapphire fiber is one of the most serious issues in R&D items. Investigation and human resources are necessary. We also check the other material, for example, silicon.

33. 3. b-KAGRA 3.7 Risk management Measurement and simulation of
(a) Vibration via heat link (P=2, S=2, R=4)
Measurement and simulation of
shield vibration and heat link transfer function
Careful design
(b) Vertical spring in cryostat (P=2, S=2, R=4)
Development should be in progress.
Here are items, the risk factor is 4. Vibration via heat links is a problem. We need Measurement and simulation of shield vibration and heat link transfer function. After that, we design heat link carefully. The second item is the vertical spring in cryostat. Develoment should be in progress.

34. 3. b-KAGRA 3.7 Risk management Risk 4
(c) Operation of Type-A with cryogenic payload
(P=2, S=2, R=4)
No test outside the mine
We should learn many lessons in R&D.
(d) Short installation time
for mirrors (3 months) (P=2, S=2, R=4)
We should learn many lessons in R&D
(or adjust the schedule of DRMI experiment).
The third item is the operation of Type-A with cryogenic payload. Although the careful test should be necessary before we install them in mine, the test outside the mine is impossible. We should learn many lessons in R\&D and need some tests at Kamioka site. The fourth item is short installation time for mirrors, only 3 month for all mirrors ! We should learn many lessons in R&D or adjust the schedule of DRMI experiment.

35. 3. b-KAGRA 3.7 Risk management Risk 4 Other items (P=2, S=2, R=4)
Some troubles in cryogenic experiment
Assembling payload
Baffles for scattered light in cryostat
Control and damping system
Procurement of key component
Unexpected long cooling and heating time
Unexpected extra heat load
Electric noise from cryostat
Lack of space in cryostat
And there are other risks.

36. Appendix Design changes after first external review None
The last part is the appendix. The first item is the design changes after first external review.
On the first external review, the cryogenic payload is not discussed. Thus, there are no changes.

37. Appendix B. Items that have been reduced in cost None
The second one is items that have been reduced in cost. Again,
on the first external review, the cryogenic payload is not discussed. Thus, there are no items.

38. Appendix C. Human resources Before installation of payload,
Technical staffs, Graduate students, Post docs
Experiment of 1/4 cryostat : 3 persons
Other R&D items : 7 persons
Cryogenic experiment apparatus for R&D
KEK (two small vacuum flasks for liquid helium)
ICRR (CLIK, small cryocooler from Mio lab)
Other ?
OK, this is the last and one of the most serious issues; human resources. Before installation of payload, we need engineers, graduate students, and post doc. For experiment of ¼ cryostat, 3 persons are necessary. For, other R&D items, 7 persons are necessary. In this phase, cryogenic apparatus are also necessary. As long as I know, there are two small vacuum flasks in KEK and CLIK and small cryocooler in ICRR. But I am afraid that we need more apparatus.

39. Appendix C. Human resources
In installation of payload : Technical staffs
3 persons for 1 payload
Jul Feb : 3 persons for payload
Feb Dec : 6 persons for payloads
If persons for Type-A are taken into account,
Jun Jul : 3 (Type-A)
Jul Oct : 3 (payload) + 3 (Type-A)
Nov Feb : 3 (payload) + 9 (Type-A)
Feb May 2016 : 6 (payload) + 6 (Type-A)
Jun Dec : 6 (payload)
In the phase of installation of payload, the engineers are necessary. For a payload, 3 persons must work.
Therefore, 3 persons must work for cryogenic payloads between July 2015 and February 2016.
6 persons must work for cryogenic payloads between February 2016 and December 2016.
If persons for Type-A are taken into account, the summary is as follows. 12 persons are necessary from November 2015 to May 2016.

40. Thank you for your attention !
That’s all. Thank you for your attention.

41. 3. b-KAGRA Current status
R&D items in progress
Simulation for initial cooling time (Sakakibara)
Thermal and mechanical simulation (Koike)
Mechanical simulation (including thermal noise)
(Sekiguchi)
Simulation for transfer function of heat link (Aso)
Calculation of thermal noise (Yamamoto)
Sapphire fibers (Shibata, Ushiba, Chen, Suzuki)
Material selection for mass and wire (Tokoku)
Reflectance of DLC (Sakakibara)
Vertical spring in cryostat (Ishizaki, Sekiguchi)
And many other R&D investigations are in progress.

42. 3. b-KAGRA
3.3 Schedule
Mar : 1/4 cryostat will arrive at Kashiwa.
Apr Sep : Experiment of 1/4 prototype
- Sep : R&D items (sapphire fibers ...)
Sep : Final design for payload
Jul Mar : Procurement
Jun Sep :
Installation and commissioning for end mirrors
Nov Dec :
Installation and commissioning for front mirrors
This is the outline of the timeline. On March of 2013, quarter cryostat will arrive at Kashiwa and the experiment starts. We should proceed with investigation for some R&D items, for example, sapphire fibers. These investigation is continued until September of On this month, the final design will be fixed. From July of 2014 and March of 2015, we will procure the payload. From June of 2015 to September of 2016, the payloads for end mirrors are installed and commissioned. The same procedure for the front mirrors are repeated from November of 2015 to December of 2016.