Ernest Potenziani - Academia.edu (original) (raw)
Papers by Ernest Potenziani
Journal of Applied Physics, 1988
10B, 11B, 57Fe, and 59Co spin-echo NMR experiments have been performed for naturally abundant and... more 10B, 11B, 57Fe, and 59Co spin-echo NMR experiments have been performed for naturally abundant and 10B-enriched Nd2Fe14B and Nd2Fe14−xCox B (x≤0.7) at 1.3 and 4.2 K for frequencies from 10 to 300 MHz. The Fe hyperfine field (HF) values in the Nd2Fe14B compound and their assignment to the six iron sites are the following: 302(e) 320(c) 325(k1), 334( j1), 352(k2), and 378( j2) kOe. The substitution of Co for Fe decreases the HF at the Fe nuclei at j2, k2, j1, k1, and c sites while no obvious change in the HF at the e site nor at the B nuclei has been found. The spin-echo amplitude corresponding to the Fe(k2) site line decreases with increasing Co content. A complex 59Co spectrum is found in the frequencies between 150 and 260 MHz with a strong peak around 250 MHz. These results confirm that Co atoms have a strong preference to enter the k2 site.
Physical Review B, 1987
The 10B, 11B, and 57Fe hyperfine field distributions for 10enriched Nd15Fe77B8 and Nd15Fe77-xCoxB... more The 10B, 11B, and 57Fe hyperfine field distributions for 10enriched Nd15Fe77B8 and Nd15Fe77-xCoxB8 (x<12) were measured by spin-echo NMR at 1.3 and 4.2 K for frequencies from 10 to 70 MHz. Using 98% 10B enrichment makes the 57Fe resonances more pronounced, which enabled us to precisely determine the hyperfine field values. As suggested by the spin-echo amplitudes and the frequency shifts caused by Co substitution, the assignment of the measured hyperfine fields of Nd15Fe77B8 to the six Fe sites is tentatively the following: 378(j2), 352(k2), 334(j1), 325(k1), 320(c), and 302(e) kOe. The substitution of Co for Fe decreases the hyperfine fields at the Fe nuclei at the j2, k2, j1, k1, and c sites, while no obvious change in the hyperfine field at the e-site Fe nuclei nor at the B nuclei has been found. The spin-echo amplitude corresponding to the Fe(k2) site line decreases drastically with Co content. These results demonstrate that Co atoms have a strong preference to substitute for the Fe(k2) atoms.
Structural mass as a function of field for two different period-to-bore ratios. 56 43 Maximum fie... more Structural mass as a function of field for two different period-to-bore ratios. 56 43 Maximum field attainable in three twister structures as a function of twist period to working space ratio. 56 44 Maximum field attainable as a function of segment thickness/period ratio for the octagonal structure of Fig. 41b. 57 45 Exploded view of a twister prototype. 57 46 Addition of fields of two nested twisters to form a wiggler field. 58 1 Magnetic circuits and their electrical counterparts. 10 2 Magnetic flux paths of Fig. 4(a).
Journal of Applied Physics, Apr 15, 1985
The hysteresis loops of three commercial magnets with room temperature energy products greater th... more The hysteresis loops of three commercial magnets with room temperature energy products greater than 25 MGOe were obtained over the temperature range 4.2–700 K in applied magnetic fields extending to ±90 kOe. Two of the samples are of the Sm2Co17 type and the other of Nd2Fe14B. The magnetic parameters extracted from the hysteresis loops are compared with each other and with those of a previously measured 2‐17 specimen. The temperature dependencies of intrinsic coercivities and remanences of the 2‐17’s are similar, as are the magnitudes of the remanences. However, the magnitudes of the intrinsic coercivities differ greatly. For example, at 300 K they are 6.4, 13.4, and 24 kOe, a ratio of approximately 1:2:4. The value for Nd2Fe14B is 11.3 kOe at 300 K. The temperature coefficient of coercivity ranges from −0.225%/K to −0.405%/K for the 2‐17’s and −1.09%/K for Nd2Fe14B. The room temperature energy products are 26 and 27 MGOe for the 2‐17’s and 32 MGOe for Nd2Fe14B. The temperature coefficients of energy prod...
MRS Proceedings, 1987
ABSTRACTMany devices that employ magnetic fields are encumbered by massive solenoids with their e... more ABSTRACTMany devices that employ magnetic fields are encumbered by massive solenoids with their equally bulky power supplies or by inefficient permanent-magnet structures designed for use with obsolescent magnet materials. This paper describes how the high-energy product materials are employed in several structures to afford mass and bulk reductions of an order of magnitude or more. Also discussed are novel designs that are not attainable with the older materials such as the alnicos. Substitution of solenoids with permanent magnets also eliminates considerable energy consumption and the attendant problems arising from generation of heat. In many cases, all this is accomplished within leakage-free systems. Among the designs described are: nuclear magnetic resonance imagers; cylindrical solenoidal field structures for klystrons and nonperiodic field TWT's; cylindrical field structures with arbitrary axial gradients for advanced gyrating beam sources; annular field sources for high...
Journal of Applied Physics, 1984
We have extracted the coercivities, remanences, and anisotropy fields from M‐H loop measurements ... more We have extracted the coercivities, remanences, and anisotropy fields from M‐H loop measurements on four permanent magnets of composition Sm1−xErx(Co,Fe,Cu,Zr)7.3 with x=0, 0, 0.2, 0.4. Room‐temperature coercivities iHc were observed which are higher than those of representative commercial 2 : 17 magnets by factors ranging from three to six. Room‐temperature coercivity to anisotropy field ratios are extraordinarily high, ranging from 0.15 to 0.25. A pulsed magnetizing field of 60 kOe was insufficient to produce the latter result which was obtained only after exposure of the sample to 90 kOe. All of the specimens displayed demagnetization curves linear over the entire second quadrant, with slopes μr ranging from 1.1 to 1.4. Excellent temperature coefficients α with a good energy product (BH)max were obtained for x=0.4, with α=0.01%/K from 300 to 425 K and 0.005%/K from 225–300 K and (BH)max=16 MGOe.
Journal of Applied Physics, 1990
The high-energy rare-earth permanent magnets afford iron-free wiggler and twister field sources w... more The high-energy rare-earth permanent magnets afford iron-free wiggler and twister field sources with greater field strengths in less massive structures than are possible when iron pole pieces and flux conductors are employed. However, the iron-free configurations have been notoriously difficult to adjust, as operational efficiency is very sensitive to the influence of small defects incurred in magnet manufacture and assembly.
Journal of Applied Physics, 1990
Unclassified Unclassified Unclassified UL '~ 7540-0-0-5500 Standard Forrm 98 29eo 26.89
Journal of Applied Physics, 1988
The use of permanent magnets in brushless motors and generators is highly desirable in that they ... more The use of permanent magnets in brushless motors and generators is highly desirable in that they have great potential for reducing weight and increasing e ciency. A self shielding cylindrical permanent magnet assembly has been designed and was found to produce high fields at the outer magnet surface and very little flux leakage into the interior rotor space. Construction of this as sembly is simplified because it is composed of magnets of simple triangular cross sections, which have only four distinct orientations. The self shielding nature of the design obviates any need for ferromagnetic material for flux shaping or shielding, thus simplifying greatly the mathematical analysis of the design and reducing its weight and bulk. Finite element methods are used to analyze a hypothetical permanent magnet rotor assem bly with regard to various design parameters.
Journal of Applied Physics, 1987
Permanent-magnet annoiar, longitudinal field sources John P. Clarke, Ernest Potenziarci li, and H... more Permanent-magnet annoiar, longitudinal field sources John P. Clarke, Ernest Potenziarci li, and Herbert A. LeupokJ US Army Electronics ... novel permanent-magnet configurations are described which can bring about weight savings by providing a eross-sectionally uniform field ...
Journal of Applied Physics, 1987
With the increasing demands upon millimeter/microwave devices with regard to miniaturization, pow... more With the increasing demands upon millimeter/microwave devices with regard to miniaturization, power, frequency range, etc., there have arisen requirements for strong (kOe) magnetic fields of unusual shape, confined to small regions by permanent magnetic configurations of minimal bulk. The present work describes several novel permanent magnet structures that produce uniform fields of up to several kOe confined to spaces with thicknesses an order of magnitude smaller than the other two dimensions. Such structures are potentially useful for focusing ribbonlike electron beams in devices such as orotrons. The structural principles used to accomplish this can also be used to shorten long, but efficient, (permanent magnet) transverse field sources, without loss of field strength or incurrence of flux leakage. Examples of proposed structures are discussed and analyzed.
Journal of Applied Physics, 1991
A structure derived from a hemispherical source design is compared with several more conventional... more A structure derived from a hemispherical source design is compared with several more conventional permanent magnet and electromagnetic configurations as sources for extended interaction klystrons. It is found that mass reductions of 50-80 percent are often realized when the hemispherical source replaces any of the others. Such reductions afford considerable performance improvements in radars, radios, and jammers, especially in airborne
Journal of Applied Physics, 1993
Page 1. Multi-Tesla permanent magnet field sources Herbert A. Leupold, Anup S. Tilak, and Ernest ... more Page 1. Multi-Tesla permanent magnet field sources Herbert A. Leupold, Anup S. Tilak, and Ernest Potenziani II US Army, Electronics Technology and Devices Laboratory SLCET-ET-H, Fort Monrnozcth, New Jmq 077034601 ...
Journal of Applied Physics, 1988
Recent developments in permanent-magnet materials have made possible several novel high-field sou... more Recent developments in permanent-magnet materials have made possible several novel high-field sources, with great potential application in mm/microwave/optical technology. However, even the crude approximations to such structures, which are needed to make their manufacture viable, entail as many as 72 pieces with eight distinct shapes. It has recently been shown that simpler equivalents of some of the structures can be
IEEE Transactions on Magnetics, 1996
To obtain the high fields at short periods characteristic of G IRON wiggler type free electron la... more To obtain the high fields at short periods characteristic of G IRON wiggler type free electron lasers (FELs), we have designed a circularly polarized radiation source or twister that operates on the same principle. As in the wiggler, the field sources are poles produced on surfaces of iron saturated by externally applied axial magnetic fields. Because of the much higher saturation magnetization of iron, the pole densities are greater than can appear on permanent magnet surfaces and therefore can produce higher magnetic fields. Such structures are compared to permanent magnet twisters with regard to field strength, bulk and ease of manufacture.
IEEE Transactions on Magnetics, 1989
IEEE Transactions on Magnetics, 1989
This paper presents a method for compensating for nonunifonnity of magnetization in a yokeless pe... more This paper presents a method for compensating for nonunifonnity of magnetization in a yokeless permanent magnet designed for clinical applications of nuclear magnetic resonance (NMR). The field generated by the magnet is confined within the magnetic material without the use of an external yoke. The method involves two steps: compensation in the individual magnet components and shiiruning of the assembled magnet. This paper discusses the first step, and, in particular, the compensation of the lowest hannonics of the field.
IEEE Transactions on Magnetics, 1984
Four permanent magnet specimens of the form Sml-xErx (C O , F~, C~, Z~)~.~~ have been investigate... more Four permanent magnet specimens of the form Sml-xErx (C O , F~, C~, Z~)~.~~ have been investigated w i t h regard t o coercivity, remanence, energy product, and temperature coefficients of remanence and energy product at temperatures ranging from 200K t o 800K. The results are compared with previously measured SmCo5 and SmCo17 type material, with respect to suitability for use a t temperatures above 400K. All the specimens measured were superior t o the SmCo5 and Sm2Co17. The most sui table material of a1 1 was found t o be ErOe4 (Co,Fe,Cu,Zr)7.22 with the following properties a t 500K: Br = 9.3 kG, IHC = 9.4 kOe, (BH)max=16.5MGOe a = 0.004%/KY = O.O08%/K.
IEEE Transactions on Magnetics, 1986
Several permanent-magnet structures for whole-body nuclear magnetlc resonance diagnostics are des... more Several permanent-magnet structures for whole-body nuclear magnetlc resonance diagnostics are described and compared. All provide a field of 1. 5 kOe over wurkin volumes of about 0.9 m3 without the use of e H ectrical solenoids or bulky puwer su plies. A previously pro osed ferrite mudel now we$s more than 11 tons. by using rnpre unorth ox configurations employin rare earth permanent magnets, the same per P orrnance can be attained with as little as 3.6 tons of material. "Imaging News, " Diagnatic Imaging 7(1), 10 January 1985 J. H. Battucletti a d T. A. Knox, IEEE Trans.
Journal of Applied Physics, 1988
10B, 11B, 57Fe, and 59Co spin-echo NMR experiments have been performed for naturally abundant and... more 10B, 11B, 57Fe, and 59Co spin-echo NMR experiments have been performed for naturally abundant and 10B-enriched Nd2Fe14B and Nd2Fe14−xCox B (x≤0.7) at 1.3 and 4.2 K for frequencies from 10 to 300 MHz. The Fe hyperfine field (HF) values in the Nd2Fe14B compound and their assignment to the six iron sites are the following: 302(e) 320(c) 325(k1), 334( j1), 352(k2), and 378( j2) kOe. The substitution of Co for Fe decreases the HF at the Fe nuclei at j2, k2, j1, k1, and c sites while no obvious change in the HF at the e site nor at the B nuclei has been found. The spin-echo amplitude corresponding to the Fe(k2) site line decreases with increasing Co content. A complex 59Co spectrum is found in the frequencies between 150 and 260 MHz with a strong peak around 250 MHz. These results confirm that Co atoms have a strong preference to enter the k2 site.
Physical Review B, 1987
The 10B, 11B, and 57Fe hyperfine field distributions for 10enriched Nd15Fe77B8 and Nd15Fe77-xCoxB... more The 10B, 11B, and 57Fe hyperfine field distributions for 10enriched Nd15Fe77B8 and Nd15Fe77-xCoxB8 (x<12) were measured by spin-echo NMR at 1.3 and 4.2 K for frequencies from 10 to 70 MHz. Using 98% 10B enrichment makes the 57Fe resonances more pronounced, which enabled us to precisely determine the hyperfine field values. As suggested by the spin-echo amplitudes and the frequency shifts caused by Co substitution, the assignment of the measured hyperfine fields of Nd15Fe77B8 to the six Fe sites is tentatively the following: 378(j2), 352(k2), 334(j1), 325(k1), 320(c), and 302(e) kOe. The substitution of Co for Fe decreases the hyperfine fields at the Fe nuclei at the j2, k2, j1, k1, and c sites, while no obvious change in the hyperfine field at the e-site Fe nuclei nor at the B nuclei has been found. The spin-echo amplitude corresponding to the Fe(k2) site line decreases drastically with Co content. These results demonstrate that Co atoms have a strong preference to substitute for the Fe(k2) atoms.
Structural mass as a function of field for two different period-to-bore ratios. 56 43 Maximum fie... more Structural mass as a function of field for two different period-to-bore ratios. 56 43 Maximum field attainable in three twister structures as a function of twist period to working space ratio. 56 44 Maximum field attainable as a function of segment thickness/period ratio for the octagonal structure of Fig. 41b. 57 45 Exploded view of a twister prototype. 57 46 Addition of fields of two nested twisters to form a wiggler field. 58 1 Magnetic circuits and their electrical counterparts. 10 2 Magnetic flux paths of Fig. 4(a).
Journal of Applied Physics, Apr 15, 1985
The hysteresis loops of three commercial magnets with room temperature energy products greater th... more The hysteresis loops of three commercial magnets with room temperature energy products greater than 25 MGOe were obtained over the temperature range 4.2–700 K in applied magnetic fields extending to ±90 kOe. Two of the samples are of the Sm2Co17 type and the other of Nd2Fe14B. The magnetic parameters extracted from the hysteresis loops are compared with each other and with those of a previously measured 2‐17 specimen. The temperature dependencies of intrinsic coercivities and remanences of the 2‐17’s are similar, as are the magnitudes of the remanences. However, the magnitudes of the intrinsic coercivities differ greatly. For example, at 300 K they are 6.4, 13.4, and 24 kOe, a ratio of approximately 1:2:4. The value for Nd2Fe14B is 11.3 kOe at 300 K. The temperature coefficient of coercivity ranges from −0.225%/K to −0.405%/K for the 2‐17’s and −1.09%/K for Nd2Fe14B. The room temperature energy products are 26 and 27 MGOe for the 2‐17’s and 32 MGOe for Nd2Fe14B. The temperature coefficients of energy prod...
MRS Proceedings, 1987
ABSTRACTMany devices that employ magnetic fields are encumbered by massive solenoids with their e... more ABSTRACTMany devices that employ magnetic fields are encumbered by massive solenoids with their equally bulky power supplies or by inefficient permanent-magnet structures designed for use with obsolescent magnet materials. This paper describes how the high-energy product materials are employed in several structures to afford mass and bulk reductions of an order of magnitude or more. Also discussed are novel designs that are not attainable with the older materials such as the alnicos. Substitution of solenoids with permanent magnets also eliminates considerable energy consumption and the attendant problems arising from generation of heat. In many cases, all this is accomplished within leakage-free systems. Among the designs described are: nuclear magnetic resonance imagers; cylindrical solenoidal field structures for klystrons and nonperiodic field TWT's; cylindrical field structures with arbitrary axial gradients for advanced gyrating beam sources; annular field sources for high...
Journal of Applied Physics, 1984
We have extracted the coercivities, remanences, and anisotropy fields from M‐H loop measurements ... more We have extracted the coercivities, remanences, and anisotropy fields from M‐H loop measurements on four permanent magnets of composition Sm1−xErx(Co,Fe,Cu,Zr)7.3 with x=0, 0, 0.2, 0.4. Room‐temperature coercivities iHc were observed which are higher than those of representative commercial 2 : 17 magnets by factors ranging from three to six. Room‐temperature coercivity to anisotropy field ratios are extraordinarily high, ranging from 0.15 to 0.25. A pulsed magnetizing field of 60 kOe was insufficient to produce the latter result which was obtained only after exposure of the sample to 90 kOe. All of the specimens displayed demagnetization curves linear over the entire second quadrant, with slopes μr ranging from 1.1 to 1.4. Excellent temperature coefficients α with a good energy product (BH)max were obtained for x=0.4, with α=0.01%/K from 300 to 425 K and 0.005%/K from 225–300 K and (BH)max=16 MGOe.
Journal of Applied Physics, 1990
The high-energy rare-earth permanent magnets afford iron-free wiggler and twister field sources w... more The high-energy rare-earth permanent magnets afford iron-free wiggler and twister field sources with greater field strengths in less massive structures than are possible when iron pole pieces and flux conductors are employed. However, the iron-free configurations have been notoriously difficult to adjust, as operational efficiency is very sensitive to the influence of small defects incurred in magnet manufacture and assembly.
Journal of Applied Physics, 1990
Unclassified Unclassified Unclassified UL '~ 7540-0-0-5500 Standard Forrm 98 29eo 26.89
Journal of Applied Physics, 1988
The use of permanent magnets in brushless motors and generators is highly desirable in that they ... more The use of permanent magnets in brushless motors and generators is highly desirable in that they have great potential for reducing weight and increasing e ciency. A self shielding cylindrical permanent magnet assembly has been designed and was found to produce high fields at the outer magnet surface and very little flux leakage into the interior rotor space. Construction of this as sembly is simplified because it is composed of magnets of simple triangular cross sections, which have only four distinct orientations. The self shielding nature of the design obviates any need for ferromagnetic material for flux shaping or shielding, thus simplifying greatly the mathematical analysis of the design and reducing its weight and bulk. Finite element methods are used to analyze a hypothetical permanent magnet rotor assem bly with regard to various design parameters.
Journal of Applied Physics, 1987
Permanent-magnet annoiar, longitudinal field sources John P. Clarke, Ernest Potenziarci li, and H... more Permanent-magnet annoiar, longitudinal field sources John P. Clarke, Ernest Potenziarci li, and Herbert A. LeupokJ US Army Electronics ... novel permanent-magnet configurations are described which can bring about weight savings by providing a eross-sectionally uniform field ...
Journal of Applied Physics, 1987
With the increasing demands upon millimeter/microwave devices with regard to miniaturization, pow... more With the increasing demands upon millimeter/microwave devices with regard to miniaturization, power, frequency range, etc., there have arisen requirements for strong (kOe) magnetic fields of unusual shape, confined to small regions by permanent magnetic configurations of minimal bulk. The present work describes several novel permanent magnet structures that produce uniform fields of up to several kOe confined to spaces with thicknesses an order of magnitude smaller than the other two dimensions. Such structures are potentially useful for focusing ribbonlike electron beams in devices such as orotrons. The structural principles used to accomplish this can also be used to shorten long, but efficient, (permanent magnet) transverse field sources, without loss of field strength or incurrence of flux leakage. Examples of proposed structures are discussed and analyzed.
Journal of Applied Physics, 1991
A structure derived from a hemispherical source design is compared with several more conventional... more A structure derived from a hemispherical source design is compared with several more conventional permanent magnet and electromagnetic configurations as sources for extended interaction klystrons. It is found that mass reductions of 50-80 percent are often realized when the hemispherical source replaces any of the others. Such reductions afford considerable performance improvements in radars, radios, and jammers, especially in airborne
Journal of Applied Physics, 1993
Page 1. Multi-Tesla permanent magnet field sources Herbert A. Leupold, Anup S. Tilak, and Ernest ... more Page 1. Multi-Tesla permanent magnet field sources Herbert A. Leupold, Anup S. Tilak, and Ernest Potenziani II US Army, Electronics Technology and Devices Laboratory SLCET-ET-H, Fort Monrnozcth, New Jmq 077034601 ...
Journal of Applied Physics, 1988
Recent developments in permanent-magnet materials have made possible several novel high-field sou... more Recent developments in permanent-magnet materials have made possible several novel high-field sources, with great potential application in mm/microwave/optical technology. However, even the crude approximations to such structures, which are needed to make their manufacture viable, entail as many as 72 pieces with eight distinct shapes. It has recently been shown that simpler equivalents of some of the structures can be
IEEE Transactions on Magnetics, 1996
To obtain the high fields at short periods characteristic of G IRON wiggler type free electron la... more To obtain the high fields at short periods characteristic of G IRON wiggler type free electron lasers (FELs), we have designed a circularly polarized radiation source or twister that operates on the same principle. As in the wiggler, the field sources are poles produced on surfaces of iron saturated by externally applied axial magnetic fields. Because of the much higher saturation magnetization of iron, the pole densities are greater than can appear on permanent magnet surfaces and therefore can produce higher magnetic fields. Such structures are compared to permanent magnet twisters with regard to field strength, bulk and ease of manufacture.
IEEE Transactions on Magnetics, 1989
IEEE Transactions on Magnetics, 1989
This paper presents a method for compensating for nonunifonnity of magnetization in a yokeless pe... more This paper presents a method for compensating for nonunifonnity of magnetization in a yokeless permanent magnet designed for clinical applications of nuclear magnetic resonance (NMR). The field generated by the magnet is confined within the magnetic material without the use of an external yoke. The method involves two steps: compensation in the individual magnet components and shiiruning of the assembled magnet. This paper discusses the first step, and, in particular, the compensation of the lowest hannonics of the field.
IEEE Transactions on Magnetics, 1984
Four permanent magnet specimens of the form Sml-xErx (C O , F~, C~, Z~)~.~~ have been investigate... more Four permanent magnet specimens of the form Sml-xErx (C O , F~, C~, Z~)~.~~ have been investigated w i t h regard t o coercivity, remanence, energy product, and temperature coefficients of remanence and energy product at temperatures ranging from 200K t o 800K. The results are compared with previously measured SmCo5 and SmCo17 type material, with respect to suitability for use a t temperatures above 400K. All the specimens measured were superior t o the SmCo5 and Sm2Co17. The most sui table material of a1 1 was found t o be ErOe4 (Co,Fe,Cu,Zr)7.22 with the following properties a t 500K: Br = 9.3 kG, IHC = 9.4 kOe, (BH)max=16.5MGOe a = 0.004%/KY = O.O08%/K.
IEEE Transactions on Magnetics, 1986
Several permanent-magnet structures for whole-body nuclear magnetlc resonance diagnostics are des... more Several permanent-magnet structures for whole-body nuclear magnetlc resonance diagnostics are described and compared. All provide a field of 1. 5 kOe over wurkin volumes of about 0.9 m3 without the use of e H ectrical solenoids or bulky puwer su plies. A previously pro osed ferrite mudel now we$s more than 11 tons. by using rnpre unorth ox configurations employin rare earth permanent magnets, the same per P orrnance can be attained with as little as 3.6 tons of material. "Imaging News, " Diagnatic Imaging 7(1), 10 January 1985 J. H. Battucletti a d T. A. Knox, IEEE Trans.