Overview of the CMOS Cameras Used at JET

Overview of the CMOS cameras used at JET

Itziar Balboa, Scott Silburn, Guy Matthews, Dave Kinna, Bernhard Sieglin, Thomas Eich, Michael Faitsch, Tim May-Smith, Alexander Huber, Valentina Huber, Marcus Price, Graham Jones and JET contributors*

* See the author list of “X. Litaudon et al 2017 Nucl. Fusion 57 102001″ Date: 26.06.18 Contents

.Joint European Torus (JET) . Camera diagnostics at JET . Applications: - Plasma Imaging - Infrared Thermography . Summary

I. Balboa | 2018 EIROforum workshop: CMOS Sensors| CERN | 26.06.18 | Page 2 JOINT EUROPEAN TORUS (JET)

 JET is a research facility that houses the world largest tokamak for fusion research  Goals: Develop a new form of renewable energy to supply electricity  How: Capturing the energy released in fusion reactions  Plasma confined by magnetic fields

JET ENVIRONMENT . High Magnetic Fields (1-3 Teslas) . High Current to >4.106 Amps . High Current Transients > 108 A/s . Neutrons and gamma rays

DIAGNOSTICS: . Instrumentation to a) Measure plasma properties b) Evaluate plasma performance c) Investigate plasma instabilities, etc.. c) Protect components inside tokamak . Total: ~ 100 diagnostics . Camera Diagnostics: 32

I. Balboa | 2018 EIROforum workshop: CMOS Sensors | CERN| 26.06.18 | Page 3 JOINT EUROPEAN TORUS (JET)

JET TOKAMAK inside the TORUS HALL (38 m2 x 25m (height)) BIOLOGICAL SHIELD WALL - protection from radiation

I. Balboa | 2018 EIROforum workshop: CMOS Sensors| CERN | 26.06.18 | Page 4 Inside the JET tokamak

 Inside of tokamak and superimposed with a photo of the plasma  Tokamak is made of individual components known as “Tiles”  Main tile materials: Beryllium, Bulk Tungsten and Tungsten coated carbon tiles

I. Balboa | 2018 EIROforum workshop: CMOS Sensors | CERN | 26.06.18 | Page 5 Camera diagnostics at JET

• Camera diagnostic = camera + filter + optics + software • Goal: Imaging the plasma/tiles from optical windows at the vacuum boundary • Applications: - Displaying the plasma pulse (see video) - Machine protection – keeping within thermal limits in order to prevent damage to tiles inside the vessel - Characterizing events within the plasma - Monitoring of plasma impurities - Infrared Thermography for quantitative scientific analysis • Total: 32 systems

I. Balboa | 2018 EIROforum workshop: CMOS Sensors | CERN| 26.06.18 | Page 6 Camera diagnostics at JET

• Location: - Most systems are next to the tokamak (inside Torus Hall )

- Recently: selection of cameras systems installed outside Torus Hall

• Why installing systems outside the TH?: - Radiation damage – camera reliability affected by neutrons/gammas - Examples given in the next slides

Name of presenter | Conference | Venue | Date | Page 7 CMOS camera systems at JET

. In the past CMOS camera systems have been used for - High Speed Imaging (visible) - Quantitative Infrared Thermography (Hybrid CMOS)

. New CMOS camera systems have been installed for -Visible plasma imaging to support operation (qualitative) - Machine protection (quantitative)

I. Balboa | 2018 EIROforum workshop: CMOS Sensors | CERN| 26.06.18 | Page 8 Plasma Imaging

Example of a camera located outside the TH and used to display the plasma pulse SPECIFICATIONS KLDT-O5WB Supplier ZWO Sensor Type Colour CMOS (1/1.2”) Model ASI174MC-COOL Pixel Array 1936 x 1216 (2.3Mega Pixels) https://astronomy-imaging-camera.com Pixel Pitch 5.86µm Sensor Size 11.3 x 7.1 mm2 Exposure Range 32µs - 300s Interface USB 3.0 ADC 12 bits

I. Balboa | 2018 EIROforum workshop: CMOS Sensors | CERN| 26.06.18 | Page 9 Plasma Imaging - Video

Video of a plasma pulse (speed x16)

I. Balboa | 2018 EIROforum workshop: CMOS Sensors | CERN| 26.06.18 | Page 10 High Speed Imaging

- Function: Identify fast events and structures during the plasma pulse (qualitatively) SPECIFICATIONS Diagnostic Names: KL8 & KLDT-E5WE Supplier PHOTRON Model FASTCAM APX-RS Sensor Type CMOS Monochrome Pixel Array 1024 x 1024 Pixel Pitch 17µm https://photron.com/ Sensor Size 17.4 x17.4 mm2 Frame Rate (FPS) 60 (full frame) 250,000 (128 x 16) Interface IEEE 1394 (FireWire) ADC 10 bits

I. Balboa | 2018 EIROforum workshop: CMOS Sensors | CERN| 26.06.18 | Page 11 High Speed Plasma Imaging

Identical cameras in different locations (inside TH and outside TH) to identify plasma structures

Name of presenter | Conference | Venue | Date | Page 12 Infrared Thermography - Functionality

• Measuring Surface Temperature of Plasma Facing Components

• Calculating Heat Fluxes

• Goal: Understand the plasma load onto plasma facing components to allow performance optimisation

I. Balboa | 2018 EIROforum workshop: CMOS Sensors | CERN| 26.06.18 | Page 13 Infrared Thermography – Specifications

SPECIFICATIONS Diagnostic Name: Diagnostic Name: KL7 KL3B, KL9s Supplier CEDIP FLIR Sensor Type InSB (FPA1) InSB (FPA1) Pixel Array 640 x 512 320x 256 Pixel Pitch 25 30 Sensor Size 16 x 12.8 mm2 9.6 x 1.68 mm2 https://www.flir.com NETD2 < 20mK < 20mK Frame Rate 60Hz (Full Frame) 380Hz (Full Frame) Sensor 77K 77K Temperature Wavelength 1-5.4µm 1.5-5.0µm Response Interface CamLink Gigabit Ethernet ADC 14 bits 14 bits 1FPA: Focal Plane Array 2NETD: Noise Equivalent Temperature Difference I. Balboa | 2018 EIROforum workshop: CMOS Sensors | CERN| 26.06.18 | Page 14 Infrared Thermography – Magnetic Fields

• Magnetic fields can induced eddy currents which affect camera electronics • Cameras exposed to: - DC magnetic field < 0.2T - Time varying magnetic field: 0.25T/s • Measures taken against effects of magnetic field: i. Placing the camera inside a magnetic shielding box - Shield box: material: soft iron thickness: 30mm weight: 250kg ii. Removal of ferrites from sensor & cooler electronics

I. Balboa | 2018 EIROforum workshop: CMOS Sensors | CERN| 26.06.18 | Page 15 Infrared Thermography – Magnetic Fields

Installation of a camera inside magnetic shielding box

I. Balboa | 2018 EIROforum workshop: CMOS Sensors | CERN| 26.06.18 | Page 16 Infrared Thermography – Applications

Group Selfie - Infrared image of the inside of the tokamak - Colours represent Temperatures

Temperature of inner & outer wall Beryllium tiles Temperature range: 200-1200C Spatial resolution: tens of millimetres per pixel

I. Balboa | 2018 EIROforum workshop: CMOS Sensors | CERN| 26.06.18 | Page 17 Infrared Thermography –Tiles in-vessel

JET Tokamak Divertor or Exhaust

Castellated structure Materials: - Bulk Tungsten -Tungsten coated

Spatial resolution < 2mm per pixel HEAT FLUX PROFILE (#91735 @ 48.4s) Pulse 91735 Stack C

I. Balboa | 2018 EIROforum workshop: CMOS Sensors | CERN| 26.06.18 | Page 18 Infrared Thermography – Calibration

- Calibration of the entire camera system using a hot source inside the vessel - Goal : Convert Raw signal to Temperature - Hot source held by robotic arm and pointing towards optical window - Calibration only takes place when there are no operations (maintenance & servicing)

Robotic Arms Infrared image of hot source

Hot Source I. Balboa | 2018 EIROforum workshop: CMOS Sensors | CERN| 26.06.18 | Page 19 Infrared Thermography – NUC

• Focal Plane arrays (FPA) show - Variations in gain and offset for each individual pixel

• Result: noise pattern added to the image

• Correction: Non-Uniformity correction (NUC)

• NUC Set up: - relative large hot source in front of the camera (20cm2)  taking measurements at two temperatures - Gold mirror in front of the sensor

I. Balboa | 2018 EIROforum workshop: CMOS Sensors | CERN| 26.06.18 | Page 20 Infrared Thermography – Failure Mode

 Failure: Loss of communication with Device

 Impact: No acquisition  Loss of Data during the JET pulse (1 JET pulse costs ~€20k)

 Cause: Ancillary electronics are damaged by neutron/gamma-rays

I. Balboa | 2018 EIROforum workshop: CMOS Sensors | CERN| 26.06.18 | Page 21 Infrared Thermography – Failure Mode

 Level of Damage – Escalation: Rebooting Camera  Uploading firmware  FPGA Board Replacement  Camera Replacement

 Firmware Upload: - This is done via serial port of the camera - Frequency: ~ 1 month - Neutron yield: 1.6 x 1018 n (see reference [1]) - Neutron fluence in the area: 4.3 x 109 n/cm2 (see reference [1])

 Moving Forward: Two solutions - Solution 1: Remove ancillary electronics from Torus Hall - Solution2: Relocate camera system to outside the Torus Hall

Reference [1]: “Response of the imaging camera to hard radiation during JET operation”, A. Huber et. Al, Fusion Engineering and Design 123 (2017) 669-673

Name of presenter | Conference | Venue | Date | Page 22 Infrared Thermography – Solution 1

IN-HOUSE ALTERNATIVE SOLUTION  SPLIT THE CAMERA DEVICE IN TWO BIOLOGICAL SHIELD WALL IN TORUS HALL OUTSIDE TORUS HALL SENSOR & COOLER ONLY FRAME GRABBER

. In this configuration the sensor is inside the tokamak building but the frame grabber is located outside the tokamak building. Detector connected to frame grabber via optical link . This configuration has been tested successfully for three months

I. Balboa | 2018 EIROforum workshop: CMOS Sensors | CERN| 26.06.18 | Page 23 Infrared Thermography – Solution 1 SPECIFICATIONS Diagnostic Name: KL9B Supplier SEMICONDUCTOR DEVICES Model Pelican-D Sensor Type InSB (FPA) Pixel Array 640 x 512 Pixel Pitch 15µm Sensor Size 9.6 x 7.68 mm2 Frame Rate (FPS) 300 Hz (full frame) http://www.scd.il Sensor Temperature 77k (Stirling Cooler) Wavelength 3.6 – 4.9µm Response

I. Balboa | 2018 EIROforum workshop: CMOS Sensors | CERN| 26.06.18 | Page 24 Infrared Thermography – Solution 2

Concept: BIOLOGICAL OUTSIDE TOKAMAK BUILDING TOKAMAK BUILDING SHIELD WALL SELECTED CAMERA SYSTEMS

PENETRATION TUBE 1 Total: 5 cameras sys. MIRROR + RELAYS PENETRATION TUBE 2 Total: 2 systems + pyrometers

- Project Cost: < 700,000€ - This solution can only be applied to a selection of cameras - Two penetrations drilled in the bioshield for two separate views: - Wide angle view - Divertor view

I. Balboa | 2018 EIROforum workshop: CMOS Sensors | CERN| 26.06.18 | Page 25 Infrared Thermography – Solution 2

Installation layout for the Wide Angle (40 metres optical path)

I. Balboa | 2018 EIROforum workshop: CMOS Sensors | CERN| 26.06.18 | Page 26 Infrared Thermography – Solution 2

Installation layout for the Divertor view (approx. 30m optical path)

I. Balboa | 2018 EIROforum workshop: CMOS Sensors | CERN| 26.06.18 | Page 27 Machine Protection – new cameras

-Measure surface temperatures from tiles inside the vessel -Prevent damage of tiles from plasma heat loads SPECIFICATIONS Diagnostic Name: Diagnostic Name: KLDT-P5WA KLDT-P5TB Supplier New Imaging Technologies Model Widy SWIR 640U-ST Widy SWIR 640V-ST Sensor InGaAs Monochrome

Pixel Array 640 x 512 http://new-imaging-technologies.com/en Pixel size 15 x 15µm

Frame 200fps (Full Frame)

Wavelength Range 900-1.7µm QE(>70%)

Interface USB 2.0 USB 3.0

ADC 14 bits

Name of presenter | Conference | Venue | Date | Page 28 Machine Protection – new cameras

• Historically cameras used for machine protection: CCD type • New protection cameras being commissioned • Advantage with CMOS/hybrid CMOS types: - Large pixel size - makes it less sensitive to radiation damage - Flexible windowing capability - variable (higher) frame rate - Anti-Blooming

I. Balboa | 2018 EIROforum workshop: CMOS Sensors | CERN| 26.06.18 | Page 29 Summary

• Overview of the camera systems with CMOS/Hybrid CMOS at JET including: - Applications - Failure mode - Alternative solutions

Name of presenter | Conference | Venue | Date | Page 30