Tunable High Power Excimer Lasers Physics and Technology

Hofman.Th,Tittel.F.K 慶熙大學校 레이저 工學硏究所 1991 레이저공학 Vol.2 No.-

The development of scalable high power lasers in the UV -visible range and ultrashort high brightness laser sources impact a number of key technologies. Experiments of scaling the e-beam pumped XeF(C →A) laser system to the 1 Joule/pulse output level at a 1 Hz repetition rate are described. Recent progress in the amplification of tunable ultrashort laser pulses in the visible spectrum, utilizing the broadband XeF(C →A) excimer transition, is also reported. Scaling experiments of an injection controlled XeF(C →A) laser pumped by an intense short pulse electron beam have been performed. Using a multi-component high pressure gas mixture comprised of F₂,N₃,F, Xe, Kr, and Ar, a specific laser energy output density of 1.7 J/l with an intrinsic efficiency of 1.3% were achieved at 486.8 nm, corresponding to an output energy of 0.8 J. Futhermore, the short pulse electron beam excited XeF(C →A) excimer laser was demonstrated to be continuously tunable between 450 nm and 530 nm with an output line width as narrow as 0.001 nm. Improved laser performance of 1.2 J per pulse and, in particular, repetitive operation of up to 1 Hz using a compact, gas fiow(~5.7m/s) system has been achieved. In addition, the broad gain bandwidth, which is significantly larger than those available from organic dyes and UV excimer lasers, makes the XeF(C →A) system a suitable medium for amplfication of ultrashort laser pulses to the terawatt level in the blue green. The feasibility of developing an ultrahigh brightness laser source in the visible based on the XeF(C →A) transition of 490nm, 250fs pulses yielded a maximum energy of 275mJ and laser power in the terrawatt range. An upper limit of 0.4% was found for the ASE energy level. The beam quality of the amplified pulses was determined as 1.3 times diffraction limited, considering the torus-shaped beam profile. The amplification of 250fs pulses with ~2nm bandwidth made use of only a fraction of the XeF(C →A) gain bandwidth of 60 nm. It is expected that pulses of much shorter duration, such as the blue-green 10fs pulses demonstrated by Schoenlen et al. or frequency doubled, modelocked Ti : sapphire pulses can be amplified in this excimer system, possibly further increasing the peck output power. In fact, modeling of the XeF(C →A) transition suggests that both the gain and the saturation energy density do not change significantly for injection pulse duration as short as 50fs. Scaling of the XeF(C →A) excimer system has been demonstrated successfully for nanosecomd system, and therefore the design of electron-beam pumped, large aperture systems, as demonstrated for the KrF excimer should also be applicapable to the XeF(C →A) excimer amplifier, increasing the performance of this system even further.

Integrated Model of Power Electronics, Electric Motor, and Gearbox for a Light EV

Hofman, Isabelle,Sergeant, Peter,Van den Bossche, Alex,Koroglu, Selim,Kesler, Selami The Korean Institute of Power Electronics 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.6

This study presents a model of a drivetrain for an integrated design of a light electric vehicle (EV). For the drivetrain of each front wheel of the single-person, battery-powered EV tricycle consists of a battery, an inverter, and an outer rotor permanent magnet synchronous motor (PMSM), which is connected to an in-wheel gearbox. The efficiency of the inverter, motor, and gearbox is analyzed over the New European Driving Cycle. To calculate the losses and efficiency of the PMSM, the power electronics in the inverter and gearbox are used. The analytical models provide a fast, but less accurate result, useful for optimization purposes. To accurately predict the efficiency of the PMSM, a finite element model is used. The models are validated by test setups. Correspondingly, a good agreement between the measurements and the calculated results is achieved. A parameter study is performed to investigate the influence of the detailed component parameters (i.e., outer rotor radius, gear ratio, and number of pole pairs and stator slots) on the average efficiency of the drivetrain.

A CLASSIFICATION OF UNIQUELY DIFFERENT TYPES OF NUCLEAR FISSION GAS BEHAVIOR

HOFMAN GERARD L.,KIM YEON SOO Korean Nuclear Society 2005 Nuclear Engineering and Technology Vol.37 No.4

The behavior of fission gas in all major types of nuclear fuel has been reviewed with an emphasis on more recently discovered aspects. It is proposed that the behavior of fission gas can be classified in a number of characteristic types that occur at a high or low operating temperature, and/or at high or low fissile burnup. The crystal structure and microstructure of the various fuels are the determinant factors in the proposed classification scheme. Three types of behavior, characterized by anisotropic $\alpha$-U, high temperature metallic $\gamma$-U, and cubic ceramics, are well-known and have been extensively studied in the literature. Less widely known are two equally typical low temperature kinds: one associated with fission induced grain refinement and the other with fission induced amorphization. Grain refinement is seen in crystalline fuel irradiated to high burnup at low temperatures, whereas breakaway swelling is observed in amorphous fuel containing sufficient excess free-volume. Amorphous fuel, however, shows stable swelling if insufficient excess free-volume is available during irradiation.

Integrated Model of Power Electronics, Electric Motor, and Gearbox for a Light EV

Isabelle Hofman,Peter Sergeant,Alex Van den Bossche,Selim Koroglu,Selami Kesler 전력전자학회 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.6

This study presents a model of a drivetrain for an integrated design of a light electric vehicle (EV). For the drivetrain of each front wheel of the single-person, battery-powered EV tricycle consists of a battery, an inverter, and an outer rotor permanent magnet synchronous motor (PMSM), which is connected to an in-wheel gearbox. The efficiency of the inverter, motor, and gearbox is analyzed over the New European Driving Cycle. To calculate the losses and efficiency of the PMSM, the power electronics in the inverter and gearbox are used. The analytical models provide a fast, but less accurate result, useful for optimization purposes. To accurately predict the efficiency of the PMSM, a finite element model is used. The models are validated by test setups. Correspondingly, a good agreement between the measurements and the calculated results is achieved. A parameter study is performed to investigate the influence of the detailed component parameters (i.e., outer rotor radius, gear ratio, and number of pole pairs and stator slots) on the average efficiency of the drivetrain.

A global issue: preservation of digital objects

Hans Hofman 한국기록관리학회 2002 한국기록관리학회지 Vol.2 No.2

Synthesis of polymer membranes of different porosity and their application for phenol removal from liquid phase

Magdalena Hofman-Bieniek,Robert Pietrzak,Katarzyna Jasiewicz 한국화학공학회 2014 Korean Journal of Chemical Engineering Vol.31 No.2

Preparation of polymeric membranes based on polyethersulfone (PES) modified by adding different amountsof a pore-forming agent (PVP) is presented, and potential application of the membranes obtained for removal of phenolfrom the liquid phase is examined. The addition of various amounts of PVP has been shown to bring about changesin the content of the surface oxygen groups, but has no significant effect on the chemical character of the groups andacidic groups dominate. Filtration by phenol solution leads to significant changes in the total content of surface oxides;however, the acidic groups remain dominant. Membranes characterized by higher porosity exhibited more stable andhigher rejection ratio for phenol removal. Although all the membranes were characterized by similar rejection ratiosfor phenol removal, the cake resistance (Rc) and pore resistance (Rp) values were found to depend significantly onthe structure and porosity of the membrane applied for filtration.

Results from the Dutch Noise Innovation Program Road traffic (IPG) and Roads to the Future Program (WnT)

Rob Hofman,Jasper van der Kooij 한국소음진동공학회 2003 한국소음진동공학회 국제학술대회논문집 Vol.2003 No.8

A CLASSIFICATION OF UNIQUELY DIFFERENT TYPES OF NUCLEAR FISSION GAS BEHAVIOR

Gerard Leonard Hofman,YEON SOO KIM 한국원자력학회 2005 Nuclear Engineering and Technology Vol.37 No.4

The behavior of fission gas in all major types of nuclear fuel has been reviewed with an emphasis on more recentlydiscovered aspects. It is proposed that the behavior of fission gas can be classified in a number of characteristic types thatoccur at a high or low operating temperature, and/or at high or low fissile burnup. The crystal structure and microstructure ofthe various fuels are the determinant factors in the proposed classification scheme. Three types of behavior, characterized byanisotropic -U, high temperature metallic -U, and cubic ceramics, are well-known and have been extensively studied in theliterature. Less widely known are two equally typical low temperature kinds: one associated with fission induced grain refinementand the other with fission induced amorphization. Grain refinement is seen in crystalline fuel irradiated to high burnup at lowtemperatures, whereas breakaway swelling is observed in amorphous fuel containing sufficient excess free-volume. Amorphousfuel, however, shows stable swelling if insufficient excess free-volume is available during irradiation.

오두막 집(하이타)

아담 호프만(Adam Hofman),스튜디오 플루서(사진) 현대건축사 2024 월간 CONCEPT Vol.- No.297

Modeling of Interaction Layer Growth between U-Mo Particles and an Al Matrix

김연수,G.L. Hofman,류호진,박종만,A.B. Robinson,D.M. Wachs 한국원자력학회 2013 Nuclear Engineering and Technology Vol.45 No.7

Interaction layer growth between U-Mo alloy fuel particles and Al in a dispersion fuel is a concern due to the volumeexpansion and other unfavorable irradiation behavior of the interaction product. To reduce interaction layer (IL) growth, asmall amount of Si is added to the Al. As a result, IL growth is affected by the Si content in the Al matrix. In order to predictIL growth during fabrication and irradiation, empirical models were developed. For IL growth prediction during fabrication andany follow-on heating process before irradiation, out-of-pile heating test data were used to develop kinetic correlations. Twoout-of-pile correlations, one for the pure Al matrix and the other for the Al matrix with Si addition, respectively, weredeveloped, which are Arrhenius equations that include temperature and time. For IL growth predictions during irradiation, theout-of-pile correlations were modified to include a fission-rate term to consider fission enhanced diffusion, and multiplicationfactors to incorporate the Si addition effect and the effect of the Mo content. The in-pile correlation is applicable for a pure Almatrix and an Al matrix with the Si content up to 8 wt%, for fuel temperatures up to 200 ºC, and for Mo content in the rangeof 6 – 10wt%. In order to cover these ranges, in-pile data were included in modeling from various tests, such as the USRERTR-4, -5, -6, -7 and -9 tests and Korea’s KOMO-4 test, that were designed to systematically examine the effects of thefission rate, temperature, Si content in Al matrix, and Mo content in U-Mo particles. A model converting the IL thickness tothe IL volume fraction in the meat was also developed.