Development of KAGRA Cryogenic Payload Takahiro Miyamoto ICRR, D1 1

Contents Cryogenic prototype payload – Cryogenic payload – Performance test of prototype payload Initial tilt adjustment system – Status of cryogenic payload – 1 st cryogenic payload was Assembled – Summary of 1 st cryogenic payload assembly Cryogenic displacement sensor – Concept of cryogenic displacement sensor – LED and PD cooling test Summary 2

Contents Cryogenic prototype payload Cryogenic prototype payload – Cryogenic payload – Performance test of prototype payload Initial tilt adjustment system Initial tilt adjustment system – Status of cryogenic payload – 1 st cryogenic payload was Assembled – Summary of 1 st cryogenic payload assembly Cryogenic displacement sensor – Concept of cryogenic displacement sensor – Status of development of sensor Summary 3

Cryogenic payload Platform (GAS filter) Vibration isolation in the vertical direction for heat links Marionette + recoil mass This stage has the initial tilt adjustment system. Intermediate mass + recoil mass The main mirror is hung from this stage. Sapphire mirror + recoil mass This is main mirror of interferometer. Cryogenic Payload 4 A. Hagiwara

We tested the performance using a prototype payload. Test items Test items Dynamic range and resolution of tilting adjustment of the mirror Performance test of prototype payload 5 どうゆう試験を行うのか、 試験の概念図の様なもので 説明したほうが良い。

Moving Mass To tilt mirror, point of center of mass of marionette to move Mass on marionette. The mirror tilt must be able to be controlled well ・ slope of 1/300 in tunnel ・ strain of suspension and cryostat due to cooling ~3mrad We think mirror to need adjustment range of ~3mrad 6 Initial tilt adjustment system Performance test of prototype payload

7 One fiber Four fiber Marionett e Intermedi ate mass Dummy mirror mass 7 Initial tilt adjustment system Performance test of prototype payload

8 Mirror Laser PSD δ 2δ h ~h x PSD Laser Mirror Initial tilt adjustment system Performance test of prototype payload

Moving Mass : Cu （～ 700g) 9 Drive range of mass ： ±22mm According to left graph, we can confirm tilting range is over 3mrad. This same system is installed in 1 st cryogenic payload. +3mrad -3mrad 0 Initial tilt adjustment system Performance test of prototype payload

Status of cryogenic payload We fabricated 1 st cryogenic prototype payload without the platform. This first cryogenic payload is feedback to improve the design of KAGRA cryogenic payloads, and for measurement of performance evaluation. We need a total of 4 Cryogenic payloads. 10

1 st Cryogenic prototype payload was assembled Marionette Intermediate mass Dummy mirrorPlatform Currently, a platform prototype is in fabrication. (Rahul-san explain more detail. ) 11

Marionette Intermediate mass Dummy mirrorPlatform Main mirrors are made from sapphire to reduce thermal noise. In this test, however, we use metal dummy parts instead of sapphire suspension. (Ushiba – san and Kieran-san explain about sapphire parts.) Current state: From this assembly, we learned how to assemble payload and about issues the assembly st Cryogenic prototype payload was assembled

Summary of 1 st cryogenic prototype payload assembly From this assembly, we learned how to assemble payload and about issues the assembly. We will test performance evaluation using this 1 st cryogenic prototype payload. – Dynamic range and resolution of tilting adjustment of the mirror – Measurement of transfer function of pendulum 13

Contents Cryogenic prototype Payload – Cryogenic payload – Performance test of prototype payload Initial tilt adjustment system – Status of cryogenic payload – 1 st cryogenic payload was Assembled – Summary of 1 st cryogenic payload assembly Cryogenic displacement sensor Cryogenic displacement sensor – Concept of cryogenic displacement sensor – Status of development of sensor Summary 14

Cryogenic displacement sensor 15 Displacement sensors and actuators are installed into the recoil masses of these 2 stages. Cryogenic Payload We use the actuator and the displacement sensor to control the cryogenic payload, but these devices are cooling together with the mirror.

Specification of the cryogenic displacement sensor – Operation at very low temperature – Non-contact sensor – A large dynamic range (~1cm) – A small change in temperature can change the characteristics of the sensor 16 Cryogenic displacement sensor

In KAGRA, we use OSEM (shadow sensor) for room temperature suspension. This sensor has high sensitivity, but small dynamic range. In the case of cryogenic payload, larger misalignments may happen due to cooling, so we need to introduce a large dynamic range displacement sensor. 17 Cryogenic displacement sensor

Concept of cryogenic displacement sensor Target Photo sensor schematic We plan to use a reflection sensor(like above figure) as a displacement sensor in the cryogenic payloads. Advantage of this sensor ・ Non-contact sensor ・ A large dynamic range I have to select the usable LED and PD at cryogenic temp. 18 測定原理などいる？

LED and PD cooling test Purpose of this test – I want to check the operation of LEDs and PDs at cryogenic temperature. – I measured the efficiency change of an LED and a PD at each temperature. – We hope a small change in temperature causes a small change in the sensor characteristics. LED and PD type – LED : InAlAs[L2690], PD : InGaAs [G12180] (Hamamatsu) 19

LED and PD cooling test Setup schematic 20 ～ 2 ｃｍ Current source LED and PD could be operated at cryogenic temperature. Temperature characteristic of this LED and PD was large.

Conclusion and future work InAlAs LED and InGaAs PD could be operated at cryogenic temperature. Temperature characteristic of this LED and PD was large. For using as sensor, it is very important that we know the sensor output as a function of temperature well. Next, I test efficiency of some type LED and PD at cryogenic temperature, and I will choose best ones. 21

Contents Cryogenic prototype payload – Cryogenic payload – Performance test of prototype payload Initial tilt adjustment system – Status of cryogenic payload – 1 st cryogenic payload was Assembled – Summary of 1 st cryogenic payload assembly Cryogenic displacement sensor – Concept of cryogenic displacement sensor – Status of development of sensor Summary Summary 22

Summary 1 st cryogenic payload assembly – We completed assembly of 1 st cryogenic prototype payload except for platform. – Some tests using 1 st cryogenic payload We will develop some jigs to help with assembly Dynamic range and resolution of tilting adjustment of the mirror will be checked Measurement of transfer function of pendulum Cryogenic displacement sensor – InAlAs LED and InGaAs PD could be operated at cryogenic temperature, but temperature characteristic of this LED and PD was large. – Next, I will test the efficiency of some types of LED and PD at cryogenic temperature, and I will choose the best ones. 23 That’s all

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Back up 25

The important role of Cryogenic Payload The important role of Cryogenic Payload – Hanging the main mirror so that it is like free mass – Initial tilt adjustment of mirror – The mirror control and damping of resonant of suspension (using displacement sensor and actuator) – Heat link is attached for cooling mirror – Vibration isolation of the vibration from heat link 26 Cryogenic payload このページもいらない？

Ball Screw system ： This system is composed by screw shaft, nut and ball. This is able to transform rotation of motor into liner motion of Mass. Since the ball enter between screw shaft and nut, it is smooth that transform rotation of motor into liner motion of mass. Liquid nitrogen Development of control system of mirror Moving Mass Ball screw 27

傾き調整機構の開発 : ボールねじ機構 ボールねじ機構をするに当たり問題となりうる 点 ・ネジ部にたくさんのベアリングボールを内蔵しているため、 極低温にしたときに、ネジ部が噛んでしまい、動かなくなる可 能性がある。 ・ ・高真空 ・ 極低温仕様のために潤滑剤を用いないと寿命が著しく 短くなる。 28 ボールねじ ネジ軸にベアリングボールが内 蔵され、スムースにモーターの 回転運動を直線運動に変換でき る。よく使用される方法である。 本試験で使用したものは、市販品を 脱脂して使ったものであって、高真 空・低温用として正規に使う予定の ものは、最初からオイルレスになっ ている。 錘駆動機構の候補

126K 50K 40K 30K 変位センサ LED-PD ：冷却試験 LED(InAlAs) と PD(InGaAs) を向い合せた状態で、 LED に印加する電流による PD からの出 力を測定した。 結果 LED と PD はともに低温で壊れることなく動作することが確認できた。また、温度によ り LED に加えることのできる電流が変化することも確認された。 K 50K 292K 2K2K10K20K 40K 30K 2K2K10K 20K

30 Platform Main chain Marionette Intermediate mass mirror Recoil mass chain Heat link Cooler

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