Control for the KAGRA cryogenic payload

Transcription

1 Control for the KAGRA cryogenic payload Takafumi Ushiba Institute for Cosmic Ray Research (ICRR) The 3rd international workshop on KAGRA 21 May 2017, National Taiwan University 1

2 Contents Introduction of KAGRA cryogenic payload Sensors and actuators design Sensors and actuators test Summary 2

3 KAGRA gravitational wave detector 3-km arm interferometric gravitational detector. Located at Kamioka in Japan near Super Kamiokande. Key features: -Using underground site -Using a cryogenic mirrors Type-A suspensions 3

4 Type-A suspension for KAGRA ETMs 9-stage 14-m suspension for vibration isolation with a cryogenic mirror Suspended from 2 nd floor 14m 4-stage GAS room temperature Cryogenic Payload Credit: Masaki Ando 4

5 Cryogenic payload Inside cryostat Room temperature suspension Platform Marionette & Recoil mass Cryogenic payload Intermediate mass & recoil mass 23 kg sapphire mirror Total mass is about 200 kg Cooling with 4 cryocoolers Credit: Masaki Ando Mirror & Recoil mass 5

6 Why do we need control? Koki Okutomi There are many eigen-modes we should damp. Credit: Masaki Ando 6

7 Why do we need control Koki Okutomi High frequency modes are mainly from the cryogenic payload We should consider how to damp these modes. Credit: Masaki Ando 7

8 Contents Introduction of KAGRA cryogenic payload Sensors and actuators design Sensors and actuators test Summary 8

9 Sensors design Platform: OpLev for angular sensing OpLev for translational sensing Platform Marionette: OpLev for angular sensing OpLev for translational sensing Photosensors for six degrees of freedom Intermediate mass: Photosensors for six degrees of freedom Marionette Intermediate mass Mirror: OpLev for angular sensing OpLev for translational sensing Credit: Masaki Ando Mirror 9

10 Acuators design Platform: Four moving mass for tilt adjustment Marionette: Four moving mass for tilt adjustment Six coil-magnet actuators Intermediate mass: Six coil-magnet actuators Mirror: four coil-magnet actuators Platform Marionette Intermediate mass Mirror Credit: Masaki Ando 10

11 Moving mass Marionette Balance system on MN and PF PF moving mass: for whole suspension Moving mass MN moving mass: for main chain suspension relative adjustment between main chain and recoil chain Ball screw We also use counter weight for rough adjustment of tilt angle. Mass (Cu) Motor Credit: Masaki Ando Moving mass 11

12 Coil-magnet actuator with photosensors Magnet: Samarium-Cobalt Coil-magnet actuator with PS Efficiency: LED Mirror: 1.5 mn/a magnet Intermediate mass: 15 mn/a Marionette: 450 mn/a Front view PD Side view Two LEDs and four PDs are on one coil-magnet actuator bobbins for reducing coupling between translational motion and angular motion. We cooled several kinds of LEDs and PDs to confirm which LEDs and PDs can be used at cryogenic temperature. We calculate and estimate coil-magnet actuator noise. Credit: Masaki Ando 12

13 Estimation of electrical noises from actuators Takahiro Miyamoto Safety factor : 10 TM:1.5mN/A IM:30mN/A MN:50mN/A Low Power Coil Driver (2mA) 13

14 Contents Introduction of KAGRA cryogenic payload Sensors and actuators design Sensors and actuators test Actuator efficiency measurement Cooling test of LEDs Summary 14

15 Actuator efficiency measurement magnet coil distance Takahiro Miyamoto We get small dependence of efficiency near the peak 15

16 Actuator efficiency measurement move coil distance magnet Takahiro Miyamoto We also get small dependence of efficiency near the center 16

17 Cooling test of LEDs Check an usability of several LEDs at cryogenic temperature. Directly dunk into liquid helium(two LEDs for each model) We found two candidates for cryogenic PSs. LED PD Liquid helium LED model First one Second one 870E 1200E 1550E L L

18 Output voltage [V] Cooling test of LEDs Measure individual differences of LED efficiency Condition: inside liquid helium We decided to use 1200E for the bkagra-phase1. Further development is future investigation. 1200E m first second 1550E second first 10m 1m 1μ 10μ 100μ 1m 10m 1μ 10μ 100μ 1m 10m Supply current [A] Supply current [A] 18

19 Summary For KAGRA operation, many eigen-modes of the KAGRA cryogenic payload should be damped. Design of sensors and actuators has almost finished. We proceed tests of sensors and actuators. measure actuator efficiency decide which LED we use Further investigation is now ongoing. 19