摘要:

Thermal analyses are presented of a cylindrical target concept for the production of radioactive beams by intense, high-energy proton production beams. The basic principle is to extract heat generated internally by the production beam interactions with the target material through appropriate thermal barriers. This approach allows the target material to be operated at an elevated temperature to enhance the release of radioactivities produced by the production beam bombardment, yet remove the heat generated initially. Three classes of targets are considered: high temperature and moderate heat generation; moderate temperature and low heat generation; and low temperature and high heat generation. Various thermal barriers approaches appropriate to the combined temperature and heat removal constraints are included, such as contact thermal resistance, refractory material interfaces, and porous metal interfaces. It is shown that suitable thermal barrier approaches exist to encompass the range of target conditions expected for the production of intense beams of radioactive ions. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148235

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A laser ion source based on laser resonant ionization at the outlet of a helium jet was proposed for on-line isotope separator of the Heavy Ion Research Facility in Lanzhou, China a few years ago. An off-line test setup was built at Tsinghua University. The initial experimental results of the setup indicate that carrying neutral Na monoatoms to the outlet of a helium jet and directly ionizing the Na atoms in the helium jet beam by laser resonant ionization is very efficient. It provides an effective method for producing element selected ions with high efficiency, low background, and short transporting time. It is applicable for the separation of various elements, and is particularly useful for refractory elements. ©1997 American Institute of Physics. 

ISSN:0034-6748    

DOI:10.1063/1.1148236

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The magnetron injection gun (MIG) has been the predominant choice as the electron-beam generator in gyrodevices and it can be tuned by externally installed magnetic-field trim coils. The double-anode MIG, traditionally employed in most experiments, has the intermediate anode as an internal tuning mechanism. The single-anode design, on the other hand, is simpler to construct but lacks an internal beam tuning mechanism. The current paper describes a method to allow mechanical tuning of the MIG. Since the tip of the cathode is located in the region of the highest electric-field gradient, its extension and retraction relative to the rest of the cathode assembly provide an effective means for local electric-field profile modification and, therefore, a tuning mechanism for the electron-beam property and quality. It is demonstrated, in computer simulations and experimental tests, that the tuning mechanism adds a useful degree of freedom to the single-anode MIG for beam optimization. This method may also be applied to the double-anode design. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148237

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

For the analytical and numerical description of the emittance of a particle beam in cylindrical symmetric transport and accelerator systems often therr′plane is used, yielding a sectional emittance&egr; (r, r′).In contrast, emittance measurements are mostly taken as the projectional emittance&egr; (x, x′).As could be shown earlier, the description of a cylindrical symmetric beam in the projectionalxx′plane of phase space results in the presence of lines for each ring of particles, connecting the two corresponding points, with which the same beam is described in therr′plane. There is a very special intensity distribution along these lines, both for straight as well as for skew trajectories. It is shown here that the theoretically obtained density distribution along such a line is a weight function for the intensity measured with a slit of width&Dgr;x.For one particle it can also be interpreted as a probability function for the particle being at a certain positionx0.In view of Liouville’s theorem, the case of the two-dimensional emittance in cylindrical symmetric systems is discussed, where this law of conservation is, due to the coupling of thexandyplanes, not generally applicable. It is shown here that for an emittance measurement performed in thexx′plane, care has to be taken when choosing the slit width, since a small&Dgr;xyields a good spatial resolution, but increases the risk of missing information in the center of each connecting line. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148280

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

An ion energy loss spectrometer is designed and fabricated. The energy analyzer in our apparatus consists of 180°-cylindrical condenser electrodes equipped with the Matsuda plates. Its advantage is that focusing can be achieved by changing the electric potential applied to the Matsuda plates, which are placed at both ends of the cylindrical condenser. By this method, our energy analyzer becomes equivalent to the usual spherical condenser and its fringing field can be eliminated. The best energy resolution is 50 meV. Vibrational excitations of CO andCO2byLi+impact are measured with our spectrometer. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148238

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A simple method to determine the size of a spherical particle in an electrodynamic trap from its dynamic behavior is introduced. Contrary to common usage of electrodynamic traps, gravity is not compensated completely. The resulting oscillatory trajectory is phase shifted with respect to the driving ac field of the trap. A light barrier setup is sufficient to determine the phase lag. An analytical solution is available in closed form to yield the particle diameter from the measured phase lag. Numerical trajectory simulations support this solution. Our method is independent of the optical properties of the particle. Only the viscosity of the surrounding gas and the particle mass density have to be known for data evaluation. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148239

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The gain of microchannel plates operated with low bias voltages in the analog mode has been measured forArq+ions(3⩽q⩽16)with energies in the range from 1.5 to 154 keV/q.The results show that the gain, most likely due to the varying number of secondary electrons emitted upon impact of the detected ions, depends substantially on the charge as well as the energy of the ions. The measured gain is shown as a function of the charge state for five different ion energies per charge to assist in the interpretation of the results from the ion sources. The measured gain is also shown as a function of ion impact velocity for all measured charge states, which indicates a rather complex dependence on the ion impact velocity. The interpolated gain is also shown as a function of charge states for four different ion impact velocities. For the lowest ion impact velocity, the gain seems to increase linearly with the ions’s potential energy with the gain measured forAr16+being roughly twice as large as the gain measured for low charge states. However, for higher ion velocities, the gain surprisingly decreases for the first few charge states before it increases for higher charges(q>8)forming a minimum for an intermediate charge state. For1.4×106m/s, the measured gain ofAr3+roughly matches the gain measured forAr16+,but is roughly 60&percent; larger than the gain measured forAr8+.©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148240

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A plasma has been produced in 0.1–0.3 mTorr Ar inside a rectangularTE10mode waveguide with a cross-sectional area (6.3 cm width × 4.2 cm height) much smaller than standard waveguides (12.4 cm width ×5.6 cm height), using microwaves of 2.45 GHz and 100–260 W of power. The characteristics of the plasma and the wave propagation have been studied for the perpendicularly launched waves(k⊥B)in the ordinary like(E∥B)and extraordinary like(E⊥B)modes, where a magnetic field of about 1200 G is generated inside the waveguide by rectangular blocks of permanent SmCo magnets. The maximum electron density, as measured by a plane probe, in theE∥BandE⊥Bcases are2×1010and3×1011 cm−3,respectively, while the electron temperatures ranged between 3 and 11 eV. Experimental results obtained in the two cases are discussed and the particle trajectories are studied from a single particle theory. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148241

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A new transmission grating spectrograph for soft x-ray measurement in pulsed plasmas was designed and studied. The spectrograph has an adjustment system with three degrees of freedom, together with an electronic-controlled camera. This design makes it easy to align and use for laser-produced plasmas or the plasma focus. The spectrograph provides spatially resolved spectrum in two dimensions and has a wavelength range of 0.3–30 nm. A transmission grating was used to obtain spatially resolved spectra from plasmas produced by laser-irradiated solid target and gas filled plasma focus. Such a spectrograph is suitable for coupling with a soft x-ray streak camera or a soft x-ray charge coupled device detector for time-resolved studies. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148242

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A high-speed image converting system is described. The system is capable of display both in multiframing- and streak-mode image for a pulsed x-ray source. The system relies on a new concept without employing an image converter tube. To achieve both temporally and spatially resolved display, the image of the x-ray source is acquired with a pinhole camera and with multichannel arrayed scintillator–photomultiplier combinations, which are used complementarily. The temporal resolution is 3 ns. This system is successfully used to observe the time evolution of soft x-ray emissions around 4 Å in plasma focus discharges with puffed Ar. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148243

出版商:AIP    

年代:1997

数据来源: AIP