1. ICEC26-ICMC2016_ORAL_9-O-4C-2
Performance Studies of Cryocooler based Cryosorption pumps with Indigenous Activated Carbons 1S. Kasthurirengan, 1U. Behera, 2Vivek G.A 2Swarup Udgata 3R. Gangradey 1IISc, Bangalore, 2I Design, Pune 3IPR, Ahmedabad,
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2. ICEC26-ICMC2016_ORAL_9-O-4C-2
Outline
Need for Cryopumps for fusion systems
Development of a set up for Characterization of different types Activated Carbons from 4.5 K to 77K.
Development of a cryocooler based cryosorption pumps with with small size AC panels on its cold head.
Pumping speed measurements for N2, Ar, H2 and He on panels of different ACs ( granules, pellets, ACF-FK2 and AC knitted IPR cloth)
Analysis of experimental results & Conclusions
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3. ICEC26-ICMC2016_ORAL_9-O-4C-2
Nuclear Fusion
Fusion is the energy-production process in Sun and stars
Sun’s Core temp. is ~15 million degrees.
At such temperatures hydrogen nuclei fuse to produce Helium and Energy.
Fusion reactions are contained in a TOKAMAK, the device which uses magnetic field to confine the Plasma reactions
D + T  4He + n + Energy
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4. High Vacuum Needs of A Tokomak
High vacuum - an absolute must-
The typical high vacuum needs are for
(a) Cryostat pumping ,
(b) neutral beam pumping &
(c) torus exhaust pumping.
Typical pressures needed are
~ 10e-8 mbar (fuel injection) &
~ 10 e-10 mbar (no fuel).
Cryosorption pumps are the most suitable
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5. Characterization of activated carbons down to 4.2K
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6. Adsorber Characerization Facility for 4.5 K to 77 K
In our efforts to develop cryosorption pump, we developed an experimental set up for characterization of Adsorbents in the temp range 4.5 K to 77 K.
Built by integrating a commercial micropore analyser (upto 77K) with Two stage Cryocooler with (refrigeration power ~1.5W at 4.2K).
Systems installed & fully operational. Continuously being used for characterization of activated carbons.
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7. Adsorber Characerization Facility
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8. Typical Activated Carbons
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9. ICEC26-ICMC2016_ORAL_9-O-4C-2
Studies at 77K
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10. Adsorption at 5K for different ACs
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11. Surface Areas of Activated Carbons at 4.5 K and 77 K
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12. Development of Cryocooler Based Cryosorption Pumps
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13. Commercial Cryopanels
Cryopanels designed as per the Cryosorption pump from M/s Varian, USA.
The drawings & the photo are shown in Figure.
Cryopanels of same dimensions fabricated with different types of activated carbons.
Benchmarked against the commercial cryosorption pump
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14. AVS procedure for Pumping Speed
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15. Pumping Speed Measurement procedure
Pumping Speed Sp
Pressure P
Throughput Q
Sp = Q/P
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16. Setup of Cryocooler based Cryopump
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17. Experimental Results of Pumping Speeds
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18. Pumping Speeds for Nitrogen
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19. Pumping Speeds for Argon
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20. Pumping Speeds for Hydrogen
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21. Pumping Speeds for Helium
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22. Characterization of Activated Carbons
Using the experimental setup Characterization of activated carbons in temp range 4.5 K to 77 K has been studied.
Studies at 77 K uses nitrogen as the adsorbate and in temperature range 4.5 K to 10 K uses helium as adsorbate.
ACS 3 and ACF-FK2 have large surface areas for adsorption Compared to AC granules and pellets
ACF-FK2 and AC knitted IPR cloth perform better.
The average pore sizes range from 12 to 15 Angstroms, indicating the microporous structure of activated carbon.
Adhesive coating reduces the adsorption surface areas by about 5 to 10 %
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23. ICEC26-ICMC2016_ORAL_9-O-4C-2
Pumping Speed Studies
Compared to AC granules and pellets, ACF-FK2 and AC knitted IPR cloth perform better.
Measured pumping speeds of indigenous AC panels are some what lower than those of commercial panels.
This is due to increased wall thickness of copper sheets used for fabrication of indigenous AC panels, which in turn increases the temperatures of the panel.
Density of ACs filling on the cryopanels is an important factor influencing the performance.
Increased density filling of granules and pellets is essential for their performance improvement.
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24. ICEC26-ICMC2016_ORAL_9-O-4C-2
Conclusions
In this work, we have developed cryocooler based cryosorption pump for pumping gases susch as N2, Ar, H2 and He.
A two stage GM cryocooler with 1.5W at 4.2K has been used for this purpose.
Indigenous AC panels have been developed and used in the above setup and bench marked against the commercial panels.
Studies show that filling ACF-FK2 and Knitted IPR cloth have pumping speed performances matching to that of commercial panel.
Filling density and thickness of copper sheet used for panel fabrication play an important role in the performances.
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25. ICEC26-ICMC2016_ORAL_9-O-4C-2
Thank you !
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