Indian J. CryogVol. 30, No. 1, 2005
Fabrication of High-Tc SQUID and its Application in Measurements of Extremely Weak Magnetic Signals A. K. Gupta and Neeraj Khare National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi - 110 012
(Received March 17, 2005)
A high-Tc rf-SQUID (Superconducting Quantum Interference Device) sensor has been fabricated using natural grain boundary Josephson weak-links in Bi-Sr-Ca-Cu-O film. The film has large grains ( 20-30 m) and Tc (R=O) 104K. RF-SQUID sensor has been fabricated by patterning a hole and a microbridge on the film. The rf-SQUID shows good voltage-flux characteristics at 77K. For using SQUID as a magnetometer, it has been operated in flux-locked-loop mode at 77K. The transfer function of the SQUID is 10mV/0 and its field sensitivity 8x10-12T/Hz at 1Hz and 77K. The high-Tc rf-SQUID is used for studying the weak magnetic field from a quartz watch, destabilization of charge ordering in doped rare earth manganite, flux noise due to vortex hopping in MgB2 superconductor and for non-destructive testing.
Cryofreezers for Food S. C. Pattanayak Cryogenic Engineering Centre, IITKharagpur - 721302, India
(Received March 27, 2004)
Cryogenic freezing is a suitable technique for long term preservation of high value commodities like mushrooms, meat products, marine foods, fish and prawn. Freezing and preservation by cryogenic fluid like LN2 has already been adopted in developed countries. India, which has a considerable investment in food freezing by mechanical means, is yet to pick up the culture by adopting superior technology like cryofreezing. In the present review various aspects of cryofreezing and various types of cryofreezers available in the market and their relative advantages and disadvantages have been discussed. It has been pointed out that cryogenic freezing systems minimise the need for mechanical freezers resulting in greater process efficiency.
Keywords : Food preservation, cryofreezing.
Advances in Stirling Type Pulse Tube Cryocoolers K. G. Narayankhedkar Department of Mechanical Engineering
I.I.T., Bombay, Powai, Mumbai - 400 076
(Received April 5, 2004)
Recent advances in cryocoolers are beginning to alleviate problems such as poor reliability and increased cost. For space applications the additional requirement of high efficiency is needed, whereas for commercial applications low cost is a primary factor. The lack of a suitable cryocooler to meet the requirements of a particular application has hampered the advancement of many applications. The main problems associated with cryocoolers are: unreliability, inefficiency, size, weight, vibration, and cost. The seriousness of each of these problems depends on the application. A significant amount of cryocooler development in the last 10 years has been focused on space applications. Cryocoolers find applications in Military, Police and Security, Environmental, Commercial, Medical, Transportation, Energy, Agriculture and Biology. Developments on pulse tube cryocoolers eliminate the moving displacer in Stirling and Gifford-McMahon cryocoolers. The use of new high heat capacity materials allows Gifford-McMahon and Pulse Tube cryocoolers to reach temperatures below 4 K. A detailed review of Pulse Tube cryocoolers and indigenous developments are presented in this paper.
Performance Testing of Large Scale Cryocondensation Pump Ch. Chakrapani, S. K. Sharma, A. K. Chakraborty, M. J. Singh, G. B. Patel, S. Rambabu, P. Brijesh, U. Janardhan, S. K. Mattoo, P. K. Jaya Kumar, B. Mainak, B. Sridhar, S. Parmar, C. Nilesh, J. Prathik, U. K. Barua, M. R. Jana, P. J. Patel, V. Prahlad, N. P. Singh, C. Rotti, R.Onali, Vivek Sharma, Sanjay Shah, L. N. Gupta, Siddarth Sheth and S. Suresh Institute for Plasma Research, Bhat, Gandhinagar, Gujarat, India – 382428
Studies of Some Physical Properties of Pr Doped Y-123 High Tc Superconductors B. N. Dole* and S. S. Shah *J. E. S. Research Centre, P. G. Department of Physics
J. E. S. College, Jalna - 431 203, Maharashtra, India Department of Physics, Dr. B. A. M. University, Aurangabad - 431 004, Maharashtra, India
(Received June 14, 2005)
We have investigated Y1-xPrxBa2Cu3O7- high purity system with compositions x = 0.0, 0.2, 0.3 and 0.4. The samples of the system were prepared by nitrate evaporation route. The substitution of Pr in Y-123 compounds reduces the critical temperature (Tc) monotonically with enhancing the Pr content, but other rare earth elements do not decrease the Tc drastically. Pr is an exception for this. This anomalous behavior of Pr attracts a lot of attention of scientists, theorists, technologists and researchers. There is controversy about the valency of Pr and it is exactly not known whether it is in 3+ valence state or 4+ valence state or mixed valence state. X – ray diffraction data for the system were obtained and were close to the reports in the literature.The characterization study of the system was done by resistivity measurements. Theoretical Tc, experimental Tc and BCS Tc values were calculated and it is found that there is good matching amongst them. We have also determined the energy gap parameter(D0) theoretically, experimentally and BCS energy gap parameter from obtained Tc values and it is observed that there is good agreement amongst them. The electron phonon interaction parameter (g) is calculated for the system. It is seen that g goes on decreasing as Pr content increases. The reduction in puckering and decrease in g with increasing Pr content may result in suppression of Tc in Y-123 system.
Keywords : Nitrate evaporation route; electron phonon interaction; critical temperature; puckering.
Qualification Testing of Cryogenic Electrical Process of INSAT-2 VHRR Radiant Cooler S. C. Rastogi1, Basavaraj S. Akkimaradi1, Sant Ram1, Subramanya1, T. S. Nanjundaswamy2,
M. C. John2, E. Lakshmipati2, M. Sivaraman2 and M. S. Ramkumar2 1Thermal Systems Group, ISRO Satellite Centre Bangalore - 560 017, India,
(Received April 14, 2004)
INSAT-2 VHRR Radiant Cooler is used to cool the thermal infrared (HgCdTe) detector to cryogenic temperature in the range of 105K to 115K. Electrical processes for mounting and connecting the devices like infrared detectors, PRT sensors, thermal heaters and processes like wrapping of lead wires on FRP supports, connector wiring, hook joints, routing and anchoring were developed and a qualification test program was evolved. Devices i.e. PRT, heaters, detector-mounting PCB were tested for full life in space. The end to end wiring and instrumentation was implemented on electrical model of cooler and system level space qualification tests like electrical tests, vibration tests, electrostatic discharge (ESD) tests, thermovacuum thermal cycling tests were conducted on cooler assembly. Suitability of the materials/processes for a long mission of about 15 years life was established and also demonstrated in space application.
Liquid Nitrogen Distribution Network for the LINAC at NSC, New Delhi Suresh Babu, Anup Chaudury, S. A. Krishnan, Manoj Kumar,
R. S. Meena, Soumen Kar, Joby Antony, Jacob Chako and T. S. Datta Nuclear Science Centre, Aruna Asaf Ali Marg, New Delhi - 100 067
(Received April 15, 2004)
The cryogenic system is connected to the LlNAC through the distribution network including valve boxes to control the liquid nitrogen flow for the purpose of cooling various cryostats and operation of helium liquefier and helium gas purifier. The whole network has been installed and commissioned after conducting various online and offline performance tests. This paper explains in detail the entire network of distribution of LN2 from the source to all interconnecting application points.
Key words : LN2 Distribution Network.
Indian J. CryogVol. 30, No. 2, 2005
Adsorption Freeze Drying M. Arpita, P. Somprit and S. C. Pattanayak Cryogenic Engineering Centre, Indian Institute of Technology, Kharagpur - 721302
(Received June 21, 2005)
Freeze-drying is the process of freezing water inside the food material and then sublimating the ice into vapor at low pressure and then condensing the vapor in condenser. In the present work a freeze dryer is developed without a condenser. This function is replaced by adsorbant molecular sieve. The setup consists of an evacuated Cu cylinder of ID 10.5cm and length 34.5cm insulated by 2cm thick polyurethane foam. The test samples used in this experiment are 5.53gm and 12.2gm mass of dressed shrimp in form of a slab. The experiments are repeated for the above samples for 3.5 hrs, 4.5hrs, 5hrs, 6hrs and 7hrs of drying time and the reductions of moisture are determined by difference of weight. An analytical model is developed assuming that sublimation front moves from outside surface to inside surface. The experimental results show that for samples of 5.53gm and 12.2gm, the moisture reductions are 47.23% and 42.08% in 3.5hr drying time, 59.85% and 50.32% in 4.5hr, 64.49% and 58.75% in 5hr, 77.67% and 65.89% in 6hr, 88.78% and 75.23% in 7hr drying time. Keyword : Freeze Drying, Sublimation, Adsorbent, Analytical model.
Co-Existence of Magnetism and Superconductivity in RuSr2GdCu2O10-(Ru-1212) and RuSr2Gd1.5Ce0.5Cu2O10-(Ru-1222) Rutheno-Cuprate Compounds
V. P. S. Awana, M. A. Ansari, Anurag Gupta, R. B. Saxena and H. Kishan
National Physical Laboratory, K.S. Krishnan Marg, New Delhi - 110 012, India S. K. Malik ,Tata Institute of Fundamental Research
Homi Bhabha Road, Mumbai – 400 005, India
(Received April 5, 2004)
According to a long-term common sense, superconductivity and long-range magnetic order do not mutually co-exist within a single (thermodynamical) phase. Nevertheless, coexistence of high temperature superconductivity and magnetism was reported for a rutheno-cuprate, RuSr2(Gd0.7Ce0.3)2Cu2O10- (Au-1222) and, more recently, for RuSr2GdCu2O10- (Ru-1212). These reports have renewed the interest in the possible coexistence of superconductivity and magnetism. It is important to note that the possible coexistence of superconductivity and magnetism (in particular ferromagnetism) has been a topic of debate for decades even in the case of more homogeneous intermetallic compounds. (For a recent update of the topic, see In particular, the microscopic length scales, in terms of the superconducting coherence length, and the long-range magnetic ordering, are important. Also in high temperature superconducting compounds, large anisotropy within the unit cell and microscopic compositional variations due to different cation intermixing or the variation in oxygen content are often seen. In such a situation, the possibility of magnetic but not superconducting solid solutions coexisting microscopically with superconducting but not magnetic material cannot be ruled out without ambiguity. In the present paper, we review the existing literature critically and present our own data in terms of phase formation, structural, thermal, magnetic, electrical, spectroscopic and microscopic characterization for both Au-1212 and Au-1222. We further conclude that the coexistence of superconductivity and magnetism, in particular, the ferromagnetism at microscopic level in both these phases, need to be debated.
Key words : Ruthenocuprates, Superconductivity and Magnetism, Magnetotransport and
Magnetoresistance.
Development of an Orifice Pluse Tube Refrigerator T. K. Favas1, N. K. Mohammed Sajid1, John M. George1,
K. K. Abdul Rasheed1, K. A. Shafi1 and B. Premlet2 1Department of Mechanical Engineering, TKM College of Engineering, Kollam, Kerala - 691 005 2Department of Physics, TKM College of Engineering, Kollam, Kerala-691 005
(Received April 12, 2004)
Pulse tube refrigerators have attracted much interest because of their potential for high reliability and no moving parts at low temperatures. A single stage orifice pulse tube refrigerator has been developed and tested. The cool down characteristics with helium as working fluid is discussed in this paper.
Key words : A single stage orfice pulse tube refrigerator.
AC Susceptibility Study in Bi1.2Pb0.33Sr1.54Ca2.06Cu3Oy Superconductor S. Keshri*, S. Ravi+, V. Dayal* and P. K. Nayak+ *Dept. of Appl. Phys., B. I. T., Mesra, Ranchi – 835215 +Dept. of Phys., I. I. T., Guwahati - 781 03
(Received April 12, 2004)
The polycrystalline samples of composition Bi1.2Pb0.33Sr1.54Ca2.06Cu3Oy have been synthesized by two different methods. The synthesized samples have been characterized by their X-ray diffraction patterns and temperature variation of DC electrical resistivity down to 20K has been carried out. The samples have been identified as having single phase with a sharp transition. The results of their AC-susceptibility have been analysed using Clem’s critical state model. The effective volume fraction of the grains and the temperature dependence of the intergranular current density have been estimated.
Key words : HTS materials, superconductivity, DC resistivity, AC susceptibility
Flight Thermal Performance of VHRR Radiant Cooler on-Board Metsat Spacecraft C. K. Krishnaprakas1, S. C. Rastogi1, B. S. Akkimaradi1, D. R. Bhandari1, P. P. Gupta1, V. K. Kaila2 and H. Narayana Murthy3 1Thermal Systems Group, ISRD Satellite Centre, Bangalore - 560 017 , 2METSAT / GSAT-4, ISRD Satellite Centre, Bangalore - 560 017 3Mechanical Systems Area, ISRD Satellite Centre, Bangalore - 560 017
(Received April 14, 2004)
Passive radiant cooler has been designed and successfully realized in the METSAT spacecraft that was put into orbit on September 12, 2002 using the Polar Satellite Launch Vehicle (PSLV-C4). The radiant cooler maintains the detectors of the VHRR at cryogenic temperature for optimum performance. Mathematical models of the radiant cooler that presents a problem of nonlinear coupled conduction and radiation with partial/full radiation blockage effects and interreflections in both the diffuse and specular regimes at intervening highly polished surfaces have been developed. Thermal balance tests at simulated space conditions have been conducted to validate and refine the mathematical model. The flight performance of the radiant cooler has been very much up to satisfaction. Flight data analysis indicate that the emittance of the interior surface of the sunshield facing the cold stage patch of the radiant cooler is 0.029 at the hot case orbit in summer solstice and 0.023 at the cold case orbit in winter solstice.
Keywords : ME TSAT, polar satellite, radiant cooler.
Stirling Coolers - an Edge over the Others T. K. Jindal and P. J. Singh* *Mech. Engg. Deptt., Punjab Engg. College Chandigarh, India
(Received April 16, 2004)
Working principle of the Stirling cooler and working of different types of the Stirling coolers have been discussed. The possibility of the replacement of the conventional Rankine cycle refrigerator by Stirling refrigerator has also been investigated.
Keywords : Stirling refrigerator, Rankine cycle.
An Integrated System of Food Preservation by Cryo Freezing and Freeze Drying R. M. Khadatkar, Nilanjana Das, S. C. Pattanayak and Arpita Mondal Cryogenic Engineering Centre, lIT Khaaragpur - 721302
(Received April 8, 2004)
Out of many methods of food preservation, cryo-freezing and freeze-drying are two important methods, which have created recently lots of interest among the food scientists. The preservation by cryofreezing is achieved by very quick reduction of core temperatures of food forming very small crystals of ice and practically without any loss of weight, whereas in freeze drying it is dehydrated by sublimation of almost 95% water. Due to absence of liquid water and the low temperature achieved quickly, most of the deterioration and microbiological reaction are stopped which give final products of excellent quality with a considerable reduction in weight. However, by combining the two processes together it is possible to improve the dehydration efficiency, retaining original quality as fresh one, to improve payload in transportation and, if necessary, to make the last product into powder form. This system will be very much effective for vegetables, fruits and mushrooms and the preservation for long duration is possible at ambient temperature. This paper presents technical details of such systems, which integrate the cryofreezing, freeze drying and grinding in one operation line.
Key words : Food preservation; Cryo-freezing; Freeze-drying.
Indian J. CryogVol. 30, No. 3, 2005
Role of Vaccum Technology in Cryogenics P. Mallikarjuna Reddy, Dept. of Mech. Engg., G.P.R. Engg.College, Kurnool - 518 002, A.P. India K. Rajagopal, JNTU College of Engg., Anantapur, A.P. India
(Received April 13, 2004)
Usage of cryogenic liquids in many areas of engineering and science is growing very rapidly. After a cryogenic fluid has been liquefied and purified to the desired level, it must then be stored and transported to the users location. The ability of a cryogenic vessel or transfer line to maintain the liquefied gas in a liquid state is crucial. This attribute is usually referred to as its “holding time”. This means some sort of insulation be provided to prevent warm air from contacting the actual container. The generally accepted method of insulating the container is by taking advantage of a good vacuum’s almost nonexistent thermal conductivity. The paper describes the importance of vacuum technology for cryogenic storage-vessels and transfer-lines. A detailed description of vacuum jacketed pipe and selection procedure for cryogenic supply system is also presented.
Keywords : Dilution refrigerators, high vaccum technology.
Development of Low Purity Oxygen Plant for Blast Furnace
Air Enrichment for Plant Productivity & Coke Economy Dr. P. K. Bose Advanced Centre for Cryogenic Research
Jadavpur University Campus, Kolkata - 700 032
(Received April 7, 2004)
With the introduction of basic oxygen steel making process around the world, the need for stepping up blast furnace productivity was felt. To meet the new demands of iron and coke economy in the blast furnace operation, several processes were introduced all over the world. These have included screening, pelletising, burden distribution, humidification of blast, high blast temperature and oxyfuel injection. The choice of enriching the blast with oxygen has been questioned by those who are accustomed to use compressed oxygen at high purity for steel making process. What is needed a novel method of providing low purity oxygen supply specifically for blast furnace use. The paper suggests a model for oxygen use (along with fuel) under Indian situation for higher productivity and coke economy.
Development of SQUID Devices and Their Applications M. P. Janawadkar, R. Baskaran, Rita Saha, L. S. Vaidhyanathan, R. Nagendran,
K. Gireesan, J. Jayapandian, D. K. Baisnab and Y. Hariharan Materials Science Division, Indira Gandhi Centre for Atomic Research, Kalpakkam – 603 102
(Received April 6, 2004)
Superconducting Quantum Interference Devices (SQUIDs) represent the world’s most sensitive detectors of maganetic flux available. SQUID sensors have many applications such as in biomagnitism, in the laboratory as SQUID magnefometer, non-destructive evaluation of sub-surface defects and geophysical explorations. Recognizing the importance of varied applications of SQUID sensor, a programme has been undertaken to develop such devices. Nb-AIOx-Nb Josephson junctions and DC SQUIDs with characteristics comparable to international benchmarks have been fabricated at IGCAR.
Key words : Josephson junction, SQUID devices
Low Temperature Studies on Rare Earth Intermetallics with Exotic Ground States. Ramakrishnan Department of Condensed Matter and Material Science,
Tata Institute For Fundamental Research, Homi Bhabha Road, Mumbai - 400 005
(Received April 8, 2004)
Ternary rare earth transition metal compounds display a wide variety of phase transitions ranging from Charge Density Wave (CDW) , local moment magnetism, antiferromagnetism in the heavy fermion state, superconductivity, giant positive magneto resistance. In this review, I will focus on the observation of multiple phase transitions in RE5Ir4Si10 (RE = Er,Lu) and RE2Fe3Si5 (RE= Tm and Yb) compounds. The first series exhibit strong coupling CDW at higher temperatures which is accompanied by superconductivity or magnetic ordering at low temperature. The latter series exhibit re-entrant superconductivity in the antiferromagnetic state (Tm2Fe3Si5) and heavy fermion behavior in the antiferromagnetic state in Yb2Fe3Si5. Preliminary high pressure data indicate possible superconductivity in Yb2Fe3Si5.