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.SinghJanardhan.U, S.Rambabu, S.K.Mattoo, &NBI team

Institute for Plasma Research, Bhat, Gandhinagar, 382428.

DUCT SIDE

ELEVATION

NEUTRAL BEAM INJECTION SYSTEM

ION SOURCE SIDETOP VIEW

1

2NEUTRAL BEAM

INJECTOR AT IPR

Parameter ValueInjectionInjected PowerDelivered PowerBeam Voltage (kV)SpeciesEstimated temp.rise (keV)No. of beam linesNo. of sourcesReliability

CO, tangential5 MW1.7 MW20-80Ho, Do, He~1

11>75% of shots of0.5 MW and 1.7MW

3-D VIEW OF THE VARIOUS COMPONENTS

IN THE INJECTOR BOX

Need of Cryogenics for NBI:• To handle high throughputs of H2/D2 (50-100 torr l/s)• To maintain back ground pressure of 10-5 torr over a beam line of

~6m

High pumping speed requirement of 106 l/s

Solution: In-Vessel Cryopumps

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: LN2 distribution system, Air, Water, Electricity

Load: Cryopumps•Selection of Method and Configuration

•Why 3.8K?

•Design

• Fabrication

•Testing

Chevron baffle structure

Helium Panel

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 Cryopumps1. Chevron baffle parameters2. Helium panel parameters

OFHC copper3100 x 550 x 263 2101Al2O3 + TiO2 (60:40) (Plasma spray)

SS304 L2600 x 330 1Silver coated (Electrochemical Brush coating technique)Formed and resistance welded

SS304L seamless pipes

G-10 cryogenic grade3100 x 600 x 300

Chevron BafflesBase materialDimension (mm)NumberThickness(mm)CoatingLHe panelMaterialDimensions (mm)Thickness (mm)Coating

Manufacturing technology

DistributorsMaterialSupportsOverall pump dimensions (mm)

ValueParameter

Monte Carlo simulationParameter Values

Baffle width (cm) 2.9

Angle (deg.) 120

Inter baffle spacing (cm) 1.3

Bounce parameterParticle transmissivityPhoton transmissivity

50.231.3 x 10-3

Reflectivity of Helium panel: 0.95

Emissivity of Chevron baffle: 0.9

The design parameters lead to a pumping speed of ~10 l/s/cm2 for hydrogen, with the panel at 3.8 K, and ~ 7 l/s/cm2 for Deuterium, with the panel is cooled to temperatures ~ 4.2 K.

Fabrication of Cryopumps1) 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 jointsHelium Panel

Testing of CryopumpsProof of basic principle: CO2 pumping at 80K D2 pumping at 5KLong pulse pumping with H2 & D2 at 4.4K

5.0x10-5 1.0x10-4 1.5x10-4 2.0x10-4 2.5x10-4 3.0x10-4 3.5x10-4 4.0x10-4 4.5x10-41.2x105

1.4x105

1.6x105

1.8x105

2.0x105

2.2x105

2.4x105

2.6x105

2.8x105

Experimental speed for H2 Theoretical speed for H2 Experimental speed for D2 Theoretical speed for D2

Pum

ping

spe

ed (l

/s)

Chember pressure (Torr)

F

MFC

H2 or D2 gas To Gas Bag

F

Heat Exchanger

Flow meter

Che

vron

baf

fels

LHe

pane

l

LN2 dewarLHe Dewar

To Atmosphere

Tem

pera

ture

Se

nsor

s

Vacuum vessel

(GHe)

(GN2)

TMP

Root

Level Sensor

LN2 LHe

PiraniGuage

BA Guage

Manual Valve

Pumping speed as a function of gas throughputExperimental Set Up

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:

COLD BOXCOMPRESSOR

DEWARVALVE BOX

SUBATMHX

VSC

CRYOPUMPS

NBMP

NBRT

FROM SCMS MPSS

COOLDOWN LINE

NBI HELIUM REFRIGERATOR PLANT

MAIN

TO GAS BAG

TO GAS BAG

TO GAS BAGTO GAS BAG

OIL REMOVAL

OIL REMOVAL

cryo pumps

T1

HELIUM VESSEL

COOL DOWN LINE

RETURN LINE

L1

Return Header

Inlet Header

V3

V4V6

V7

V2

V9

V5

(0.6 bar, 3.7K) Rupture disc(7barg)

T

Temperature

Vacuum Screw

REFRIGERATOR SYSTEM

Medium pressure storage system

Cold Box

Main

Compressor

Main Dewar (1.3bar, 4.5K)

V10

Gas bag

HeaterV11VT2VT1

VR1

VR2

Return Header

Return Header

Inlet Header

cryo pumps

L1 T1

NORMAL MODE

TEST STAND MODE

V8

VALVE BOX

cryo pumps

cryo pumps

(Vacuum vessel)

(Vacuum vessel)

V12

Injector box

Test Stand

SS Recovery tank

Oil removalsystem

V13

V14

V1

compressor

PSV 3barg

Sub. Atm. Hx.

V15

PSV 19barg sensor

Process Calculations- Process Calculation note

- 110W at 3.8K with out LN2 precooling- ~170W with LN2 precooling

HELIUM REFRIGERATOR PLANT:

STANDARD HELIAL1000 + CUSTOMISED COMPONENTS FROM M/s AIRLIQUIDE-DTA

STANDARD HELIAL1000;1) MAIN COMPRESSOR WITH OIL REMOVAL SYTEM2) COLD BOXCUSTOMISED 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) 60m3 at 14 bar Carbon steel (CS) buffer tank and 15m3 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

Return Header

Inlet header

LHe Phase Separator Vessel

Cryopump

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

Cold box and Main Dewar (1500l)

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

DRAIN

CRYO HALL

EXISTING WATERBRIDGE

Gas management:

15 m3 SS tank60m3 CS tank

NRV

NRV

MV

FE

PSV

FCV

FCV

PI

LI

TI

FEFCV

PHASE SEPARATOR DEWAR (1000L)

PI

MV

APPL-I

APPL-II

APPL-III

PRV

LIQUID NITROGEN FROMMAIN TANKS (250 l/hr)

TO VENT

SCHEMATIC OF LIQUID NITROGEN DISTRIBUTION SYSTEM

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

(1.9 bar, ~83K)

Liquid Nitrogen System:Average consumption 250l/hr, beam on period 1050 l/hr, beam off period 200l/hr

Present status:1. 10 cryopumps are ready for operation2. Successful installation of all the components of the plant

and Piping3. Commissioning;

a) Conditioning of cold box and valve boxb) Main compressor start up and PID loops checkingc) Cooldown procedure start up

4. Installation of CS and SS tanks is under progress5. Prototype distribution headers for 3 Cryopumps are under testing

Proto-type LN2 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