Cryogenics for Neutral Beam Injector System Ch. Chakrapani, S.K.Sharma, A.K.Chakraborty, B.Sridhar, Vishnu.B. Patel, Siddharth Sheth, N.V.M.Rao, Mainak. B, G.B.Patel, M.J.Singh Janardhan.U, S.Rambabu, S.K.Mattoo, &NBI team Institute for Plasma Research, Bhat, Gandhinagar, 382428.
ION SOURCE SIDE 1 2 NEUTRAL TOP VIEW DUCT SIDE BEAM INJECTOR AT IPR Parameter Injection Injected Power Delivered Power Beam Voltage (kv) Species Estimated temp. rise (kev) No. of beam lines No. of sources Reliability Value CO, tangential 5 MW 1.7 MW 20-80 H o, D o, He ~1 1 1 >75% of shots of 0.5 MW and 1.7 MW ELEVATION NEUTRAL BEAM INJECTION SYSTEM
3-D VIEW OF THE VARIOUS COMPONENTS IN THE INJECTOR BOX
Need of Cryogenics for NBI: To handle high throughputs of H 2 /D 2 (50-100 torr l/s) To maintain back ground pressure of 10-5 torr over a beam line of ~6m Solution: In-Vessel Cryopumps High pumping speed requirement of 10 6 l/s
NBI CRYO PLANT: Gas Management Helium Refrigerator Load Utilities Load: Cryopumps Helium Refrigerator: Compressor, Cold box, Dewar, Valve box, Transfer lines, etc. Gas Management: Buffer tank, recovery tank, gas bags Utilities: LN 2 distribution system, Air, Water, Electricity
Load: Cryopumps Selection of Method and Configuration Why 3.8K? Design Chevron baffle structure Helium Panel Fabrication Testing
Method & Configuration selection: Cryoadsorption- Regeneration after short pulses Cryocondensation- Regeneration after long pulses-suitable for 1000s Steady state operation. - Open type (JET type) or Chevron type Open type- very high speed and high heat loads Chevron type- High speed and low heat loads- Suitable for NBI Why 3.8K? 3.8K or 4.2K- 4.2K for high back ground pressure ( low vacuum insulation) operation. 3.8K for low back ground pressure operation below 5 X 10-6 torr surrounding Helium panel(10-5 torr in the chamber).
Design of Cryopumps 1. Chevron baffle parameters 2. Helium panel parameters
Monte Carlo simulation Parameter Values Baffle width (cm) 2.9 Angle (deg.) 120 Chevron Baffles Base material Dimension (mm) Number Thickness(mm) Coating LHe panel Material Dimensions (mm) Thickness (mm) Coating Parameter Manufacturing technology Distributors Material Supports Overall pump dimensions (mm) OFHC copper 3100 x 550 x 263 210 1 Al 2 O 3 + TiO 2 (60:40) (Plasma spray) SS304 L 2600 x 330 1 Silver coated (Electrochemical Brush coating technique) Formed and resistance welded SS304L seamless pipes G-10 cryogenic grade 3100 x 600 x 300 Value Inter baffle spacing (cm) 1.3 Reflectivity of Helium panel: 0.95 Bounce parameter Particle transmissivity Photon transmissivity 5 0.23 1.3 x 10-3 Emissivity of Chevron baffle: 0.9 The design parameters lead to a pumping speed of ~10 l/s/cm 2 for hydrogen, with the panel at 3.8 K, and ~ 7 l/s/cm 2 for Deuterium, with the panel is cooled to temperatures ~ 4.2 K.
Fabrication of Cryopumps 1) Chevron baffles: a) Cu to SS TIG Brazing b) Black coating 2) Helium panel : a) SS sheets stich welding b)silver plating
Black Coated Chevron baffle TIG brazing joints Helium Panel
Testing of Cryopumps Proof of basic principle: CO 2 pumping at 80K D 2 pumping at 5K Long pulse pumping with H 2 & D 2 at 4.4K (GN2) H2 or D2 gas LHe Dewar To Atmosphere Manual Valve F MFC Pirani Guage BA Guage LHe Level Sensor Chevron baffels LHe panel Vacuum vessel Temperature Sensors Experimental Set Up Heat Exchanger F Flow meter To Gas Bag (GHe) TMP Root LN2 LN2 dewar Pumping speed (l/s) 2.8x10 5 2.6x10 5 2.4x10 5 2.2x10 5 2.0x10 5 1.8x10 5 1.6x10 5 1.4x10 5 1.2x10 5 Experimental speed for H 2 Theoretical speed for H 2 Experimental speed for D 2 Theoretical speed for D 2 5.0x10-5 1.0x10-4 1.5x10-4 2.0x10-4 2.5x10-4 3.0x10-4 3.5x10-4 4.0x10-4 4.5x10-4 Chember pressure (Torr) Pumping speed as a function of gas throughput
Helium Refrigerator Estimation of Heat loads Method for achieving 3.8K Process Design Process Calculations Fabrication of equipment & Delivery Erection & Installation Commissioning
Heat loads at 3.8K: Load on 10 Cryopumps 60W Distribution load 50W Helium Refrigerator capacity-- 110W at 3.8K
Method for 3.8K: - Vacuum Screw compressor for Creating sub atmospheric pressure - Additional sub-atmospheric heat exchanger for utilising cold enthalpy from the load
Process Design: TO GAS BAG TO GAS BAG TO GAS BAG MAIN COMPRESSOR OIL REMOVAL COLD BOX DEWAR COOLDOWN LINE VALVE BOX SUB ATM HX VSC OIL REMOVAL TO GAS BAG NBMP CRYO PUMPS FROM SCMS MPSS NBRT NBI HELIUM REFRIGERATOR PLANT
L1 L1 T1 T1 Gas bag VALVE BOX V2 V15 HELIUM VESSEL (0.6 bar, 3.7K) Rupture disc(7barg) V14 V7 V5 V8 PSV 3barg VR2 Return Header Injector box (Vacuum vessel) V12 V11 V10 Vacuum Screw Compressor Heater Sub. Atm. Hx. V9 V13 SS Recovery tank Temperature sensor T RETURN LINE V6 V4 PSV 19barg V3 VT1 VR1 VT2 cryo pumps Inlet Header cryo pumps NORMAL MODE Main compressor Oil removal system Cold Box V1 Main Dewar (1.3bar, 4.5K) Return Header cryo pumps Inlet Header cryo pumps Return Header Test Stand (Vacuum vessel) TEST STAND MODE Medium pressure storage system COOL DOWN LINE REFRIGERATOR SYSTEM
Process Calculations - Process Calculation note - 110W at 3.8K with out LN 2 precooling - ~170W with LN 2 precooling HELIUM REFRIGERATOR PLANT: STANDARD HELIAL1000 + CUSTOMISED COMPONENTS FROM M/s AIRLIQUIDE- DTA STANDARD HELIAL1000; 1) MAIN COMPRESSOR WITH OIL REMOVAL SYTEM 2) COLD BOX CUSTOMISED COMPONENTS: 1) DEWAR 2) VALVE BOX 3) SUB ATMOSPHERIC HEAT EXCHANGER 4) VACUUM SCREW COMPRESORS WITH OIL REMOVAL SYSTEM
-Sizing of Components: 1) 8g/s at 0.6bar to 1.5 bar Vacuum Screw compressor 2) Valve box with 40 l LHe phase separator Vessel 3) Sub atmospheric Heat exchanger for utilising cold enthalpy of return gas 4) 1500l main Dewar 5) 60m 3 at 14 bar Carbon steel (CS) buffer tank and 15m 3 at 6bar Stainless Steel (SS) recovery tank-gas management -Process and Instrumentation Diagram-PID: - Internal details of individual equipment - process routing - Valve size and location - Instrument type and location -Pipe/tube sizes - Safety device locations -External interfaces of individual components (Cold box, valve box, Dewar, etc.)
-Thermo-Siphon Calculation: Thermo-siphon flow design -- 20g/s with 20mm inlet dia and 25 mm outlet dia for 20m line length of inlet and out lines
LHe Phase Separator Vessel Return Header Cryopump Inlet header LIQUID HELIUM DISTRIBUTION SCHEME FOR CRYOPUMPS
Erection & Installation Main compressor and Oil removal system
Main Compressor- Rotary Screw Compressor with Variable frequency drive 40g/s- inlet 1.05 bar Outlet 14bar
Main compressor Oil removal System
Cold box and Main Dewar (1500l) Cold box
Sub-atmospheric Heat exchanger
Oil removal system for Vacuum Screw Compressor
Vacuum Screw Compressor- 8g/s (<300K at inlet) 0.6 bar to 1.5bar
Control panel VALVE BOX WITH 40l PHASE SEPARATOR VESSEL
EXISTING WATER BRIDGE CRYO HALL DRAIN
Gas management: 60m 3 CS tank 15 m 3 SS tank
Liquid Nitrogen System: Average consumption 250l/hr, beam on period 1050 l/hr, beam off period 200l/hr TO VENT FCV - FLOW CONTROL VALVE PSV - PRESSURE RELIEF VALVE NRV- NON RETURN VALVE LI - LEVEL INDICATOR MV- MANUAL VALVE FE- FLOW METER PI- PRESSURE INDICATOR TI - TEMPERATURE INDICATOR NRV PI PRV MV PI APPL-I LI FE MV PSV TI APPL-II FCV FE LIQUID NITROGEN FROM MAIN TANKS (250 l/hr) FCV APPL-III PHASE SEPARATOR DEWAR (1000L) (1.9 bar, ~83K) NRV FCV SCHEMATIC OF LIQUID NITROGEN DISTRIBUTION SYSTEM
Present status: 1. 10 cryopumps are ready for operation 2. Successful installation of all the components of the plant and Piping 3. Commissioning; a) Conditioning of cold box and valve box b) Main compressor start up and PID loops checking c) Cooldown procedure start up 4. Installation of CS and SS tanks is under progress 5. Prototype distribution headers for 3 Cryopumps are under testing
Proto-type LN 2 shielded LHe distribution header for 3 Cryopumps:
Major Issues during Plant erection, installation and commissioning Erection of support structure for valve box Valve box installation on the support structure Handling and erection of Helium transfer lines Calibration of Valves Conditioning of 2Km SS pipelines PLC programming debugging Main compressor start up Starting up of turbines Vacuum Screw compressor start up Vacuum testing of Carbon steel tank
CONCLUSION: Indigenously built large scale Cryo-condensation pumps are available for NBI system operation. The design for the in-vessel LHe distribution system for the 10 cryopumps has been done by IPR. Prototypes for inlet and return headers for 3 pumps are under testing. The LN2 lines with control and safety valves between main distribution system and loads have been fabricated in-house. Carbon steel buffer tank and SS recovery tank are erected and vacuum tests are under progress. All the GHe piping work and instrumentation work required for the Helium Refrigerator system has been prepared by IPR. The expected date of completion of Helium refrigerator system commissioning with all the components integrated is mid July 2006