T. Jaffery - Academia.edu (original) (raw)

Papers by T. Jaffery

Applied superconductivity conference,Chicago, IL (United States),23-28 Aug 1992, Sep 1, 1992

Tests have recently been performed at Fermilab and measure this behavior, in order to define oper... more Tests have recently been performed at Fermilab and measure this behavior, in order to define operational in order to measure the energy losses due to eddy currents limits for superconducting magnets under AC operation. and iron and superconductor magnetization. These While the dipole magnets for the SSC collider will not be measurements were performed on six 1.5m long model subject to fast ramp conditions, and therefore, will not be magnets and eight 15m long full scale collider dipole sensitive to conductor heating f','om AC loss energy magnets. AC losses were measured as a function of ramp rate dissipation, the magnets of the High Energy Booster will be using sawtooth ramps from 500 to 5000 Amps for both types energized/de-energized at higher rates, and wil! consequently of magnets, while bipolar studies were additionally performed be more strongly affected by AC loss mechanisms. Since the on some of the short magnets. The measured magnet voltage HEB and collider dipoles are sknilar in design, r,leasurements and current for a complete cycle are digitally integrated to of AC losses in collider dipoles yield information useful in yield the energy loss per cycle. Measurement reproducibility the design considerations of the HEB magnets. Farthermore, is typically 5%, with good agreement between long magnet measurements of AC losses in collider dipoles provide a measurements and extrapolations from short magnet means for correlating eddy current losses to observed measurement results. Magnetization loss measurements degradation of quench current as a function of ramp rate, and among similar magnet types agree to within experimental may also be useful in understanding ramp-related distortions error, while eddy current losses correlate strongly with the of field harmonics [3]. observed dependence of quench current on ramp rate. II. MEASUREMENT TECHNIQUES

IEEE Transactions on Magnetics, 1992

Several 1 meter long, 40 mm aperture model SSC dipole magnets with vertically split yokes have be... more Several 1 meter long, 40 mm aperture model SSC dipole magnets with vertically split yokes have been built and tested at Fermilab. In addition to the yoke design, these magnets were used to evaluate several variants of the collet clamps which apply prestrcss to the magnet ends. The magnets were instrumented with voltage taps for quench localization and strain gage based devices for measuring stresses, forces and deflections resulting from cooldown and excitation. Tests were carried out in a vertical dewar at temperatures from 3.8'K to 4.4"K. The quench and mechanical behavior of these magnets will be presented and magnetic field measurements will be shown. A comparison with an earlier series of magnets with horizontally split yokes will be made.

SSC l.5m model dipole magnets were built and tested at Fermilab. M:agnetic field properties were ... more SSC l.5m model dipole magnets were built and tested at Fermilab. M:agnetic field properties were studied in term of tran;sfer function variation and multipole components. The results were satisfactory. Observa-tion of periodic.ity of remanent field along the axis is also reported. 1

SSC 1.5m model dipole magnets were built and tested at Fermilab. Magnetic field properties were s... more SSC 1.5m model dipole magnets were built and tested at Fermilab. Magnetic field properties were studied in term of transfer function variation and multipole components. The results were satisfactory. Observation of periodicity of remanent field along the axis is also reported.

AC losses in full length and 1.5 m model SSC collider dipoles were successfully measured by the d... more AC losses in full length and 1.5 m model SSC collider dipoles were successfully measured by the direct observation of energy flow into and out of magnets during a ramp cycle. The measurement was performed by using two double-integrating type digital volt meters (DVM's) for current and voltage measurement. Measurements were performed for six is m long ASST magnets and five 1.5 m long model magnets, inducting one 40 mm diameter magnet. There were large variations in the eddy current losses. Since these magnets use conductors with slight deviations in their internal structures and processing of the copper surface depending on the manufacturer, it is likely that there are differences in the contact resistance between strands. Correlation between the ramp rate dependence of the,quench current and the eddy current loss was evident.

Proceedings Particle Accelerator Conference, 1995

A versatile ®eld measurement system HAL2 was developed and used for SSC magnet measurements. The ... more A versatile ®eld measurement system HAL2 was developed and used for SSC magnet measurements. The system based on V/F converter and 32 bit counters are set on a VME /modi®ed VME bus. The system was capable of measuring the high ramp rate harmonics which was a vital issue especially for the construction of SSC High Energy Booster. System description and the implementation techniques for high ramp rate application is presented together with the measurement data in SSC dipole model magnet. The measurement up to 128A=s was successful. Anomaly in the eddy current quadrupole was clearly observed.

IEEE Transactions on Magnetics, 1991

IEEE Transactions on Magnetics, 1994

ABSTRACT Dipole magnets for the R&D of SSC were built and tested at Fermilab. The magneti... more ABSTRACT Dipole magnets for the R&D of SSC were built and tested at Fermilab. The magnetic field properties were studied using short models and full scale models. Effect of coil size variation, insulation material, shimming and eddy current are discussed

submitted to MT12, …, 1991

The quench behaviors of 10 model dipole magnets for the Superconducting Super Collider have been ... more The quench behaviors of 10 model dipole magnets for the Superconducting Super Collider have been &n&d. Horisontelly split yoke, vertically split yoke and the latest 50 mm diameter design were compared in the quench cheracteristics. The excitation results showed e good progress of the R&D program. SSC magnets ten now be built with no training to the required Aeld of 0.65 T at 4.3 If.

... KH CHANG, DC KIM, IG PARK, JS SONG and CS POON Gyeongsang National University, Jinju 660-300,... more ... KH CHANG, DC KIM, IG PARK, JS SONG and CS POON Gyeongsang National University, Jinju 660-300, Korea M. CHIKAWA Kinki University Higashi ... Kobe University, Kobe 657, Japan SD CHANG, BG CHEON, JH CHO, JS KANG, CO KIM, KY KIM, TY KIM, JC LEE, SB LEE ...

In this paper we describe the operation and testing of a string of magnets comprising a full cell... more In this paper we describe the operation and testing of a string of magnets comprising a full cell of the Superconducting Super Collider (SSC). The full cell configuration composed of ten dipoles, two quadrupoles, and three spool pieces is the longest SSC magnet string ever tested. Although the tests of the full cell were undertaken after the SSC project was marked for termination, their completion was deemed necessary and useful to future efforts at other accelerator laboratories utilizing superconducting magnets. The focus of this work is on the electrical and cryogenic performance of the string components and the quench protection system with an emphasis on solving some of the questions concerning electrical performance raised during the previous two experimental runs involving a half cell configuration. KEY WORDS: Magnetic measurements, magnets: superconducting POWER TESTS OF sse MAGNET STRING LN2 r-i----:~nt~~H eater Load Distribution Box ----I Cold Box cc 20K 85 FIGURE 2.: This is the flow diagram of the plan "Pi' refrigerator which was used for the full cell tests. It was a nominal 4.5 kilowatt, 4.35 K, 100 gram/second helium refrigerator.

Conference Record of the 1991 IEEE Particle Accelerator Conference, 1991

Tests have been performed at Fermilab on 1Sm magnetic length model SCC collider dipoles using bot... more Tests have been performed at Fermilab on 1Sm magnetic length model SCC collider dipoles using both bipolar and unipolar ramp cycles. Hysteresis energy loss due to superconductor and iron magnetization and eddy currents is measured and compared as a function of various ramp parameters. Additionally, magnetic field measurements have been performed for both unipolar and bipolar ramp cycles. Measurements such as these will be used to estimate the heat load during collider injection for the SSC High Energy Booster dipoles.

Journal of Ayub Medical College, Abbottabad : JAMC

Characterization of pleural effusion into an exudate or transudate is usually the first step in d... more Characterization of pleural effusion into an exudate or transudate is usually the first step in diagnostic evaluation. Light's criteria have been universally accepted as gold standard in this regard. We wanted to see the utility of isolated pleural fluid lactic dehydrogenase level (representing one of Light's classical criteria) in characterizing pleural effusion in our setting. We also wanted to compare the accuracy of commonly used conventional criteria with Light's criteria of isolated pleural fluid lactic dehydrogenase. Patients who underwent diagnostic thoracentesis for one-year period were studied. Characterization of pleural effusions using biochemical criteria including pleural fluid protein, lactic dehydrogenase level (LDH), red blood cell (RBC) count and white blood cell (WBC) count were identified and compared with predetermined clinical criteria (gold standard). For each biochemical criteria sensitivity, specificity, positive predictive value and negative pre...

IEEE Transactions on Appiled Superconductivity, 1993

Absrracr--Tests have recently been performed at Fermilab in order to measure the energy losses du... more Absrracr--Tests have recently been performed at Fermilab in order to measure the energy losses due to eddy currents and iron and superconductor magnetization. These measurements were performed on six 1.5m long model magnets and eight 15m long full scale collider dipole magnets, AC losses were measured as a function of ramp rate using sawtooth ramps from 500 to 5000 Amps for both types of magnets, while bipolar studies were additionally performed on some of the short magnets. The measured magnet voltage and current for a complete cycle are digitally integrated to yield the energy loss per cycle. Measurement reproducibility is typically 5%, with good agreement between long magnet measurements and extrapolations from short magnet measurement results. Magnetization loss measurements among similar magnet types agree to within experimental error, while eddy current losses correlate strongly with the observed dependence of quench current on ramp rate.