Post on 24-Jun-2020
Cryogenics for particle Accelerators
Sandip Pal
VECC, Kolkata
What is Cryogenics ?• Kryo – Very cold (frost)
• Genics – to produce
• Cryogenics is a branch of physics which studies the methods to obtain temperatures below 123 K or -150°C.
• Main broad applications of cryogenics are
i) Liquefaction and separation of gases
ii) Storage and transport of gases
iii) Alternate material and fluid properties at low Temp
iv) Biological and medical applications
v) Superconductivity: Zero Ω and Magnetic flux expulsion
vi) Vacuum
vii) Cryogenic Engine
Superconducting Devices
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Applications : Gas Industry
• Liquefaction
• Separation
• Storage
• Purification
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Applications : Superconductivity
• Large scale superconducting magnet
• Superconducting RF Cavity
• MRI
• Squids
• Maglev Locomotion
• Transformers and Generators
Superconducting Cyclotron31/01/2020 IJAS-2020 VECC Kolkata 5
Outline of the talk
• Criticalities in Cryogenic Technology
• Cryogenic Fluids
• Thermodynamics
• Material properties used for cryogenics
• Generation of cryogenics
• Cryogenics for SCC at VECC
• Cryogenics for RIB e-Linac at VECC
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Design & operation criticalities
Heat budget & load type selection
Selection of liquefier and subsytems
Arrangement and Placement of systemPipelines ΔP & cryolines
High pressure gas storage & pipelines
Selection of materials in terms of strength, expansion, Heat transfer properties
Cryogenic storage, cryostat and distribution
Leak and impurity ingress especially moisture
Pressure safety system
Cryogenic instrumentation magnetic effect & thermal stress – temperature, pressure, level, flow, heater, cabling, and calibration
Thermal cycling
Asphyxiation & safety PPE
Cleaning, evacuation and purging
Water Cooling system
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Gas Management System & Purification
Useful range of cryogens
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Properties of Cryogens
Property He H2 N2 O2 Ne
Normal boiling point [K] 4.22 20.4 77.4 90.2 27.2
Critical temperature [K] 5.20 33.2 126 155 44.4
Critical pressure [bar] 2.3 13.2 34 50.8 27.2
Triple Point Temp. [K] 2.17* 14.0 63.1 54.4 24.6
Triple Point Pr. [mbar] 50.4* 72 128 1.5 432
Liq./Vap. density 7.4 53.2 176 240 127
Heat of vaporization [J.g-1] 20.4 446 199 213 86.6
Liquid viscosity [mPl] 3.3 13 152 188 124
(*) Lambda Point31/01/2020 IJAS-2020 VECC Kolkata 9
Vaporization of normal boiling cryogens under 1 W applied heat load
Cryogen [mg.s-1][l.h-1]
(liquid)[l.min-1]
(gas NTP)
Helium 48 1.38 16.4
Nitrogen 5 0.02 0.24
Using Latent Heat onlyLatent heat and enthalpy of gas
LHe from 290 to 4.2 K 29.5 lit 0.75 lit
LHe from 77 to 4.2 K 1.46 lit 0.12 lit
LN2 from 290 to 77 K 0.45 lit 0.29 lit
Amount of Cryogens Required to cool down 1kg Iron
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Cryogenics in particle accelerators
• Accelerators are electromagnetic machines, which exert forces on beams of charged particles via electric & magnetic fields for accelerating, guiding and focusing them.
• Absence of electrical d.c. resistance, or limited a.c. dissipation in superconductors opens the way to produce higher fieldsand thus higher beam energy, while containing dimensions of particle accelerators.
• Circular accelerators to handle stiffer high energy beams require increase in radius of circular path, bending radius and magnetic field - B < 2 Tesla – Iron Yoke and normal magnet B < 5.5 Tesla – Superconducting magnet of Nb-Ti wire at 4.2 K B ~ 8-10 Tesla - Superconducting magnet of Nb-Ti wire at 2 K
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Phase diagram of helium
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Helium as a cooling fluid
Phase Domain Advantages Drawbacks
Saturated He IFixed temperatureHigh heat transfer
Two-phase flowBoiling crisis
SupercriticalMonophaseNegative J-T effect
Non-isothermalDensity wave instability
Saturated Helium IILow temperatureHigh conductivityLow viscosity
Poor Dielectric StrengthCostSub-atmospheric
Pressurized Helium II
AdditionallyPrevented from air inleaksIsolation voltage ~ kV range
CostLiquid to Liquid HX
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Basic Engineering Thermodynamics
0H C
Q Q W
0CH
H C
T T
1st Law of Thermodynamics: conservation of energy
2nd Law of Thermodynamics - Clausius Law of (In)equality
Entropy is either constant or increased but never decreased
_ 1H
C
TCarnot Factor
T
Carnot factor defines the minimum amount of work necessary to extract heat at a low temperature and reject it at a higher one.
• The Carnot factor clearly demonstrates why in cryogenic system heat entering the low temperature level should be limited to the necessary minimum.
• The refrigeration work in real systems is always above the limit given by the Carnot factor due to inevitable entropy losses.
1 W at 4.2 K is equivalent to 70 W at 300 KC H
C H
Q Q
T T
ΔQH TH
ΔQC TC
ΔW∆𝑊 ≥ ∆ ሶ𝑄𝐶
𝑇𝐻𝑇𝐶− 1
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Carnot, Stirling and Eriction Cycle
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Joule-Thompson ProcessWinComp.
12
Load
HX
JT
S
TmL
mL
12
34
Q
Claude Process: combination of Brayton & JT processes
mL Q
WinComp.
12
LoadJT
S
TmL12
3
6
HX
HX
HX
Wout
Expander
4
5 7
8
3
4
5 6
7
8
For helium, inversion temperature < ambient – not possible to liquefy only by JT process31/01/2020 IJAS-2020 VECC Kolkata 16
Claude Refrigeration Cycle
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Basic Engineering Thermodynamics
Exergy analysis provides the greater insight into the influence of irreversible losses on the cycle performance.
Exergy balance equation of a thermodynamic cycle is
𝑗
ሶ𝑄𝑗 1 −𝑇0𝑇𝑗
− ሶ𝑊 + ሶ𝑚𝐿 𝐸𝑥𝐿 − 𝐸𝑥𝐼𝑁 − 𝐸𝑥𝐷 = 0
𝐸𝑥𝐷 = 𝑇0∆𝑠𝑔𝑒𝑛
𝐸𝑥 = −𝑇0 𝑠 − 𝑠0 + ℎ − ℎ0
HINV
T s hCOP
h
In reversible cycle, minimum amount of input work is required for a given rate of energy transfer (thermal) between two thermal reservoirs.
HINV
T sCOP
h
COPINV-> How many watts of input power to produce 1 W of cooling power
TH .ΔS is Isothermal compressor work
ΔH is the Expander output work
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Carnot Refrigerator & Liquefier
Carnot Refrigerator
Δs=sg-sf= 4.83W/(g/s)
Δh=hg-hf= 20.4 W/(g/s)
wREV=1430W/(g/s)
COPINV=71 W/W
Carnot Liquefier Δs=sH-sf= 28 W/(g/s)
Δh=hH-hf= 1564 W/(g/s)
wREV=6823 W/(g/s)
WC/COPINV= 100 W/(g/s)
Refrigerator transfers heat energy from a low temperature reservoir to a higher temperature reservoir
Work in refrigerator is calculated based on the difference between entropy and enthalpy of saturated vapour and liquid
Liquefier transfers heat energy from over a large varying temperature span (decreasing as fluid being cooled) to a higher temperature reservoir
Work in Liquefier is calculated based on the difference between entropy and enthalpy of fluid at ambient temperature and saturated liquid
Carnot work to liquefy 1 g/s (30 l/h) at 1 atmsaturation condition is equivalent to that for 100 W of refrigeration
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Heat Conduction in solids
Thermal Conductivity integrals of several materials [W/m]
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Thermal Radiation
• Complex system involving three heat transfer processes
– QMLI= Qrad+ Qsol+ Qres
– With n reflective layers of equal emissivity, Qrad~ 1/(n+1)
– Due to parasitic contacts between layers, Qsol increases with layer density
– Qresdue to residual gas trapped between layers, scales as 1/n in molecular regime
– Non-linear behaviour requires layer-to-layer modeling
• In practice
– Typical data available from (abundant) literature
– Measure performance on test samples
Multi-layer Insulation
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E401
E402
E403
E404
E405
E406
BUFFER
TANK
20 m3GN2
TO ATM.
DRYER
R
R
PURE H.P. CYLINDERSTORAGE
IMPURE H.P.CYLINDERSTORAGE
GAS BAG
LEAK / SYS. DISCHARGE /
BOIL OFF GAS FROM DEWAR
RECOVERYCOMP. 1
Gas bag
WarmExpander
ColdExpander
Turbo Mol. Pump
RotaryVacuum Pump
JTV 1COLD BOX
Purifier
A
LIQUID HELIUMDEWAR 1000L
LIQUID AIRDISCHARGE
A
JTV 2
RECOVERYCOMP. 2
ORM
PCV225
PCV229
CYCLECOMPRPCV223 LN2
DEWAR
23
12
3
45
6
7
8
9
S (entropy)
T (K
)
300 300
224 90
74 40
58 33
20 14
6.8 6.2
11 9
4.5 4.5
T-S diagram in liquefaction mode(Claude Cycle)
1.05 bar14 bar
5.4 bar
W/O LN2MODE
LN2MODE
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Plate-fin Heat Exchanger & Turboexpander
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Cryostat Cool Down & Warm-up
Cryostat cool down
0
50
100
150
200
250
300
29/12/04 31/12/04 02/01/05 04/01/05 06/01/05 08/01/05 10/01/05 12/01/05 14/01/05 16/01/05 18/01/05
Date (mm-dd-yy)
Tem
pera
ture
(K
)
T1
T2
T3
T4
JT Inlet T
Return T
Cool Dow n stopped for 118
hours due to non-availability
Cryostat warm up
0
50
100
150
200
250
300
350
1/3/06 3/3/06 5/3/06 7/3/06 9/3/06 11/3/06 13/3/06 15/3/06 17/3/06 19/3/06 21/3/06
Date ( mm/dd/yy)
Tem
pera
ture
(K
)
COIL TEMP T1
COIL TEMP T2
COIL TEMP T3
COIL TEMP T4
OUTLET TEMP T5
INLET TEMP T6
WARM HELIUM GAS HAS BEEN SENT
FROM THE HE-REFRIGERATOR
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Problems faced and modifications proposed
• Malfunction of CLTS temperature sensors makes control erratic – replaced with Lakeshore make Cernox sensors
• Temperature distribution of the warm and cold turbine appeared to be not usual – Process Expert intervention
• RS-485 communication should be activated
• Expander operation not optimum when cryostat connected – expander control program modified with speed feedback and seven attenuators
• 400 KVA UPS was planned for preventing helium loss
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Cold Box modification of Helial 50
Photos from top left
Cold Box lifting
Inside of cold box
Cernox sensor installation
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Refrigeration Test 250W @ 4.5K 11/01/2007, without liquid nitrogen pre-cooling
29
Modifications with introduction of Helial 2000
• Introduction of a new refrigerator/liquefier of higher capacity - Helial 2000 in parallel with Helial50
Redundancy as the existing one is old
Additional capacity to cater more refrigeration load
LHe supply for new projects in cryogenics
• Provision of Subcooler
Reduction in flash-loss and increase in liquid yield
Reduction in pressure drop and return gas flow
• Interface of 2 refrigerators for parallel operation
• Selectivity of three screw compressors – 2 nos. for new
• For simultaneous operation pressure control in new ORS
• Use of same GHe HP and LP lines and put flanges for disconnection and reconnection if required
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Capacity of Helial 2000 refrigerator
New RefrigeratorHelial 2000
Without LN2 pre-cooling (HP @ 14 bara) Flow rate- 82 g/sec
With LN2 pre-cooling
Liquefaction mode: 80 lph 176 lph
Refrigeration mode for 4.5K temp. level:
415 W 530 W(Designed)
Mixed mode at 4.5 K 360 W + 13 lph360 W + 25 lph (Designed)
360 W + 76 lph (Designed)
Cyclotron Connection switchable from one refrigerator to other almost seamlessly
Tube to tube connection inside the cold box using VBO coupling (O-ring) was avoided
Space constraints in nearby location – meticulously planned
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Overall Cryogenic System including Cryopanel which improved Vacuum Level in the Beam Chamber
R
PURE H.P. CYLINDERSTORAGE
PCV225
PCV229
PCV223
CYCLE COMPRESSORS
BUFFER 60 m3 ORM 1 Charcoal &
Oil filters
PCV289
PCV280
PCV275
ORM 2 Charcoal &Oil filters
BUFFER 60 m3
BUFFER 20 m3
C1
C2
C3
E401
E402
E403
E404
E405
E406
WarmExpander
ColdExpander
JTV 1
Helial50 cold box250W @ 4.5K50 lit/hr
A
A
JTV 2
LN2 cooling
E401
E402
E403
E404
E405
E406
WarmExpander
ColdExpander
JTV 1
Helial2000 cold box415 W @ 4.5K85 lit/hr
A
A
JTV 2
LN2 cooling
LIQUID HELIUMDEWAR 1000L
LIQUID HELIUMDEWAR 1000L
DEWAR 60L
CRYO PUMP
CRYO PANELS
SCC CRYOSTAT
From CurrentLeads
CDS valve box
HX
DSTRIBUTION BOX SUB-COOLER
To LP
Current Leads
Schematic showing existing andNew liquefier together
Old Refrigerator New Refrigerator & Distribution box with Subcooler
Glimpses of Cryogenic System of VECC
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Problems faced during commissioning
• Capacity test failed – 340 W @ 4.5K and 64 l/h
• Flow requirement higher suggested, Cv of JT and cold return valve enhanced with no effect
• Effectiveness of the first HX : prolonged temp. monitoring at inlet & outlet of CB – found OK
• Cold diversion from the LHe and cold gas return line at the side of CB interface 10.6g/s at 300K maximum
• Plug was modified by using Kel-F PCTFE material without much success – Vertical alignment is the problem
• Problem was fixed by addition of a flexible part in the vertical section to allow a free insert of the male part into the CB
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Liquefaction vs. Refrigeration Load for Helial 2000 after modification
0 100 200 300 400
0
20
40
60
80 Liquefaction vs refrigeration
Linear FitL
iqu
efa
cti
on
ra
te l/h
Refrigeration load (W)
Sandip Pal, U. Panda, A. Mukherjee, T. Maiti, and R. Dey, Indian J. of Cryo., 37(1-4), 2012, pp. 122-127.R. Dey, Sandip Pal, et. al., Indian J. of Cryo., 36(1-4), 2012, pp. 103-107.
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Cryostat Cool-down with Helial 2000
20/06/2010 04/07/2010 18/07/2010 01/08/2010
0
50
100
150
200
250
300
350
400
T1
T2
T3
T4Co
il T
em
p #
1, #
2, #
3 &
#4
(K
)
Date
Cool-down stopped
due to air ingress problem-100
-50
0
50
100
150
200
250
300
T5
T6
Inle
t &
Ou
tle
t te
mp
era
ture
(K
)
Cryostat JT
Closed
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Cool Down Result in the year 2018
-20
0
20
40
60
80
100
120
0
50
100
150
200
250
300
29/08/2018 31/08/2018 02/09/2018 04/09/2018 06/09/2018 08/09/2018 10/09/2018 12/09/2018
Leve
l (%
)
Tem
pe
ratu
re (
K)
Date
Cryostat Temp. T1, K
Cryostat Temp. T2, K
Cryostat Temp. T3, K
Cryostat Temp. T4, K
Cryostat Outlet Temp. T5, K
Cryostat Inlet Temp. T6, K
Dewar Level %
Cryostat Lower Level %
Cryostat Upper Level %
Stopped plant for compressor belt change during 9:00 hrs to 17:00 hrs
EPICS based control system
MEDM
LAN
IOC
Helial 2000
Helial 50
Overall Management
Channel Archiver for database
OPIs
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MEDM Overview Screen of the Cryogenic System
U Panda, Sandip Pal, R Dey, T Bhattacharjee, A Mandal, Control System of Cryogenic Plant for Superconducting Cyclotron at VECC, Proceedings of CYCLOTRONS 2010, MOPCP008, Lanzhou, China, 6-10 September, pp 53-55.
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Development and Testing of Variable Temperature Insert (VTI)
41
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Results of Cryogenic Temperature Sensor Calibration using VTI
0 200 400 600 800 1000
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
4.0
4.2
4.4 Calculated Temperature from Pressure
Polynomial Fit
Tem
pera
ture
co
rresp
on
din
g p
ressu
re (
K)
Saturation Vapour Pressure (mbar)
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
4.0
4.2
4.4
Temperature wrt Si Diode Voltage
Polynomial FitT
em
pera
ture
wrt
Si
Dio
de V
olt
ag
e (
K)
Variation of Temperature calculated and measured at different pressures
0 50 100 150 200 250 300 350
0
1000
2000
3000
4000
5000
6000
7000
0
500
1000
1500
2000
2500
3000 Sensor #1 Measured
Sensor #1 Calibrated
Ce
rno
x C
X-1
05
0 R
esis
tan
ce
(O
hm
s)
Temperature (K)
Sensor #2 Measured
Sensor #2 Calibrated
Error 4.2K: ±0.02K77K: ±0.25 K300K: ±0.62 K
Stability: 0.02 K
Sandip Pal, R Kar, A Mandal, A Das, S Saha, “Development of an experimental variable temperature set-up for a temperature range from 2.2 K to 325 K for cost-effective temperature sensor calibration,” Measurement Science and Technology 2017, 28 (5), 055013
42
Development of moisture Spectrometer
Pressur
e
GaugeElectronic
Module
Laser
Source
Beam
Splitte
r
Absorption
Cell
Optical
Window
Slit
Detector
with
Preamplifie
r
Detector
with
Preamplifie
r
Measureme
nt Beam
Referen
ce Beam
Mirror
Laser
Driver
Low-pass
Filter
I-V
converter 14-bit
DAC
DDS Selection of
Ramp & Sine
Gain control
16-bit
MDAC
16-bit 10
MSps ADC
LP
filter
Splitter
Detectors
I-V
Instrumentation
Amplifier
ADC
Driver S
R
D
Absorption
Cell
FPGA board
PSD
Moving
Average
NI-6534
Ethernet
Sandip Pal, Ananda Das, Sushanta Nandy, Ranjan Kar, and Jaharlal Ghosh, “Development of a near-infrared tuneable diode laser absorption spectrometer for trace moisture measurements in helium gas,” Review of Scientific Instruments, 90, 103105 (2019); https://doi.org/10.1063/1.5113968.
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PurifierTechnical Specification:• Flow Rate: 20 nm3/hr• Operating pressure: 150 bar• Min. adsorption pressure: 120 bar• Operating temperature: 77K i.e. LN2
temperature• Max. input gas impurity: 40% air impurities• Output gas purity: 99.995% or Grade 4.5 helium i.e. total air impurity < 50 ppm • Run time: 6 hours• Adsorbent: Coconut shell granular activated charcoal• Regeneration type: Thermal swing regeneration with evacuation
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Development of Helium Purifier
Sample No.
H2O (vpm)
N2
(vpm)O2
(vpm)Total
impurities
(vpm)
1 1.70 2.10 0.20 4
2 2.30 1.50 0.10 3.9
3 1.40 1.40 0.30 3.1
4 1.50 2.80 0.30 4.6
Analysis Results for input of 5% Impure gas
In collaboration with NIT Rourkella
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Critical current density of common LTC Superconductors
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Isotope Separator On Line
RIB
target 238U
fission products
Ion Source
Post-accelerator
Radioactive Ion Beam
E-Linace- g
tantalumconverter
50 MeV, 100 kW cw Superconducting Electron LinacBased on 1.3 GHz , 2K, SRF technology
Scheme of photo-fission production of RIB in ANURIB
Injector to be tested at VECC Salt Lake Campus
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E-Linac Cryomodule : SchematicCryo-insert for converting 4K Lhe to 2K
•Suspension from lid
•Cold mass supported by strong- back
•Cryogenic insert (removable from cryomodule in situ) includes
o 4K phase separator,
o 2.5g/s heat exchanger
o JT expansion valve to produce 2K liquid,
o 4K cooldown valve and
o 4K thermal intercept ckt. in a thermal siphon configuration; insert LN2 cooled thermal shield; 4K circuit for intercepts (RF couplers, beam pipe)
• Warm and cold mu-metal
• MLI for 4K & 2K cold mass
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The ACM top Assembly and ICM
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Estimated Heat Loads of E-linac Cryogenic System
5031/01/2020 IJAS-2020 VECC Kolkata
Liquid Helium plant for e-Linac at VECC
Linde LR280 With LN2 Without LN2
Refrigeration @ 4.5KGuaranteed / Actual
680 W690 W
540 W569 W
Mixed ModeGuaranteed / Actual
205W & 235 l/h205 W & 293 l/h
Liquefaction @ 1.3 bar aGuaranteed / Actual
325 l/h375 l/h
115 l/h126.5 l/h
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elinacCryomodules
Subatmospheric
Pumping system Compressor
He Dewar
Cold Box“Clean” HeliumStorage Tank
OR/GMS,
Dryer,
Purifier
“Dirty” HeliumStorage Tank
Purity monitoring(control) System
Simplified block diagram for e-Linac He Cryogenic System
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53
ColdBox
He cleanbuffer tank
Sub-atm Pump
MAIN Compr.
CryomodulesDewar
LN2tank
Purif./ Recov.Compr.
Purifier He Heater
N2 Heat Exng
CompressorBuilding
He dirty buffer tank
He Heat Exng
recovery
cooldown
coo
ldo
wn
cleaning
dumping
E-linac Cryogenic System Block Diagram
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Liquid Helium (LHe) and Sub-atmospheric (SA) Transfer Line -Schematic
LHe
DewarCold Box
ICM
Heat
Exchanger
Hx
LHe Supply Transfer line
LHe Return Transfer line
SA Return line
SA Return line
To compressor room Keep-cold
TEST AREA
Bellow joint
Control Valve
Stringer
LHe Supply/ Return
Field joint
Sub-atmospheric
Return line
26th NSCS-2017, VECC, Kolkata
LHe
Dewar
Cold
Box
ICM
TE
ST
AR
EA
LN2
Out
LN2 In
LN2 to
shield
Compressor
room
Keep
cold
Liquid Nitrogen Transfer Line Schematic
LN2
storag
e tank
Manifold-2
LN2 to shield
Manifold-3
Manifold-1
To RIB
annex
To HR Cave 1
LN2 from
shield
LN2 from
shield
Ambient
vaporizer
Vent
Purifier Cry
o-
ad
sorb
ers
Vent
Shut off valve
Control Valve
VJLHe supply
VJLHe return
VJLN2 supply
VJLN2 return
VJGN2 return
GN2 vent
Field joint
To
compresso
r room
Cross
LN2
Dewar/
Phase
separator
LN2
Dewar/
Phase
separator
SCADA for Linde Liquefier
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Conclusion
• Our work should be critically looked,
• No compromise in system development,
• Culture is important
Thank You
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