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Heat transfer coefficient in serpentine coolant passage for CCDTL

Description: A series of heat transfer experiments were conducted to refine the cooling passage design in the drift tubes of a coupled cavity drift tube linac (CCDTL). The experimental data were then compared to numerical models to derive relationships between heat transfer rates, Reynold`s number, and Prandtl number, over a range of flow rates. Data reduction consisted of axisymmetric finite element modeling where the heat transfer coefficients were modified to match the experimental data. Unfortunately, the derived relationship is valid only for this specific geometry of the test drift tube. Fortunately, the heat transfer rates were much better (approximately 2.5 times) than expected.
Date: December 31, 1998
Creator: Leslie, P.; Wood, R.; Sigler, F.; Shapiro, A. & Rendon, A.
Partner: UNT Libraries Government Documents Department

Linac design algorithm with symmetric segments

Description: The cell lengths in linacs of traditional design are typically graded as a function of particle velocity. By making groups of cells and individual cells symmetric in both the CCDTL AND CCL, the cavity design as well as mechanical design and fabrication is simplified without compromising the performance. We have implemented a design algorithm in the PARMILA code in which cells and multi-cavity segments are made symmetric, significantly reducing the number of unique components. Using the symmetric algorithm, a sample linac design was generated and its performance compared with a similar one of conventional design.
Date: September 1996
Creator: Takeda, Harunori; Young, L. M.; Nath, S.; Billen, J. H. & Stovall, J. E.
Partner: UNT Libraries Government Documents Department

Double alpha MEBT for H{sup {minus}} beam

Description: This note describes simulation studies of the H{sup {minus}} beam matching condition between a 750keV rod radio-frequency quadrupole (RFQ) and the existing Fermilab drift tube linac (DTL). The RFQ design used in this study is that of an existing RFQ designed and built by A. Schempp from IAP-Goethe University. It is assumed that the medium-energy beam transport (MEBT) line uses hardware built for a positron emission tomography (PET) project. The MEBT is made out of two Alpha magnets and seven quadrupoles and was designed by D. Larson. The beam from the exit of the RFQ is matched to the entrance in the DTL in all three dimensions. The study shows that up to 65mA of H{sup {minus}} beam can be transported and cleanly injected into the present linac.
Date: January 4, 2001
Creator: Popovic, M.
Partner: UNT Libraries Government Documents Department

Develpoment of a one-meter plasma source for heavy ion beam chargeneutralization

Description: Highly ionized plasmas are being employed as a medium for charge neutralizing heavy ion beams in order to focus to a small spot size. Calculations suggest that plasma at a density of 1-100 times the ion beam density and at a length {approx} 0.1-1 m would be suitable for achieving a high level of charge neutralization. A radio frequency (RF) source was constructed at the Princeton Plasma Physics Laboratory (PPPL) in support of the joint Neutralized Transport Experiment (NTX) at the Lawrence Berkeley National Laboratory (LBNL) to study ion beam neutralization. Pulsing the source enabled operation at pressures {approx} 10{sup -6} Torr with plasma densities of 10{sup 11} cm{sup -3}. Near 100% ionization was achieved. The plasma was 10 cm in length, but future experiments require a source 1 m long. The RF source does not easily scale to the length. Consequently, large-volume plasma sources based upon ferroelectric ceramics are being considered. These sources have the advantage of being able to increase the length of the plasma and operate at low neutral pressures. The source will utilize the ferroelectric ceramic BaTiO{sub 3} to form metal plasma. A 1 m long section of the drift tube inner surface of NTX will be covered with ceramic. A high voltage ({approx} 1-5 kV) is applied between the drift tube and the front surface of the ceramic by placing a wire grid on the front surface. Plasma densities of 10{sup 12} cm{sup -3} and neutral pressures {approx} 10{sup -6} Torr are expected. A test stand to produce 20 cm long plasma is being constructed and will be tested before a 1 m long source is developed.
Date: January 18, 2005
Creator: Efthimion, Philip C.; Gilson, Erik P.; Grisham, Larry; Davidson, RonaldC.; Yu, Simon; Waldron, William et al.
Partner: UNT Libraries Government Documents Department

Pressurized drift tubes scintillating fiber hadron calorimetry. Final report

Description: Under this contract members of the MSU high energy physics group constructed a full-scale Pressurized Drift Tube Chamber intended for the GEM muon system at the SSC. They achieved a position resolution of <90 {mu} over the full 5 m{sup 2} area of the detector. This resolution satisfied the GEM resolution requirements of <100 {mu} by a comfortable margin. Based on their SSC work they developed a new technique for creating wire supports in drift tubes with an overall placement accuracy of <20 {mu}. This technique requires only simple jigging and can be duplicated and operated at low cost. Also, they participated in the design and testing of a hadron calorimeter prototype for GEM. This work lead the authors to develop a semi-automatic welding machine to fuse together two plastic optical fibers. Copies of this machine are currently in use in the CDF endplug upgrade at Fermilab and additional copies are used widely in calorimeter and fiber-tracker construction.
Date: March 22, 1995
Creator: Bromberg, C.; Huston, J. & Miller, R.
Partner: UNT Libraries Government Documents Department

Longitudinal emittance oscillation in a superconducting drift tube linac

Description: In drift tube linacs a beam energy spread results form the finite beam size. Radial variation of the axial accelerating field induces a beam energy spread, which, in general, will accumulate as the beam passes through successive drift tubes. This paper shows that under some conditions of periodic transverse focusing and longitudinal phase focusing, the correlation between the longitudinal and transverse motion can be used to correct the energy spread. The process of achieving such a correction is first described in a simplified situation, and then demonstrated for a particular tuning using a ray-tracing program which models a low velocity and low charge state linac designed for radioactive ion beams.
Date: July 1, 1995
Creator: Kim, J.W. & Shepard, K.W.
Partner: UNT Libraries Government Documents Department

Results on intense beam focusing and neutralization from the neutralized beam experiment

Description: We have demonstrated experimental techniques to provide active neutralization for space-charge dominated beams as well as to prevent uncontrolled ion beam neutralization by stray electrons. Neutralization is provided by a localized plasma injected from a cathode arc source. Unwanted secondary electrons produced at the wall by halo particle impact are suppressed using a radial mesh liner that is positively biased inside a beam drift tube. We present measurements of current transmission, beam spot size as a function of axial position, beam energy and plasma source conditions. Detailed comparisons with theory are also presented.
Date: October 31, 2003
Creator: Roy, P.K.; Yu, S.S.; Eylon, S.; Henestroza, E.; Anders, A.; Bieniosek, F.M. et al.
Partner: UNT Libraries Government Documents Department

Long Plasma Source for Heavy Ion Beam Charge Neutralization

Description: Plasmas are a source of unbound electrons for charge neutralizing intense heavy ion beams to focus them to a small spot size and compress their axial length. The plasma source should operate at low neutral pressures and without strong externally-applied fields. To produce long plasma columns, sources based upon ferroelectric ceramics with large dielectric coefficients have been developed. The source utilizes the ferroelectric ceramic BaTiO{sub 3} to form metal plasma. The drift tube inner surface of the Neutralized Drift Compression Experiment (NDCX) is covered with ceramic material. High voltage ({approx} 8 kV) is applied between the drift tube and the front surface of the ceramics. A BaTiO{sub 3} source comprised of five 20-cm-long sources has been tested and characterized, producing relatively uniform plasma in the 5 x 10{sup 10} cm{sup -3} density range. The source was integrated into the NDCX device for charge neutralization and beam compression experiments, and yielded current compression ratios {approx} 120. Present research is developing multi-meter-long and higher density sources to support beam compression experiments for high energy density physics applications.
Date: June 1, 2008
Creator: Efthimion, P.C.; Gilson, E.P.; Grisham, L.; Davidson, R.C.; Logan, B.G.; Seidl, P.A. et al.
Partner: UNT Libraries Government Documents Department

Electrostatic field between non-concentric cylinders

Description: This report describes a closed-form solution to the electrostatic potential, and the electric field, between non-concentric cylinders, with the inner cylinder charged and the outer cylinder grounded. This problem is an abstraction of the situation of an electron beam within a drift tube. Capacitive and surface current probes on the inner wall of the outer cylinder are used to detect the asymmetry of the field when the beam is off center. The solution of this problem allows for a quantitative relationship between probe-array signals and beam deflection. probe-arrays of this type are called ''beam bugs'' at LLNL. The solution described here is suggested by the analysis presented in [3]. The essential point is that the 2D potential for a line source decreases along a radius as the logarithm of the distance. The non-concentric cylinder problem has a unique profile of this type for each ray from ({rho}, {sigma}) linking the inner cylinder at equipotential V{sub 2}, and the outer cylinder at equipotential 0.
Date: January 10, 2000
Creator: Garcia, M
Partner: UNT Libraries Government Documents Department

Status of engineering development of CCDTL for accelerator production of tritium

Description: The Coupled-Cavity Drift Tube Linac (CCDTL) is a relatively new RF accelerator structure which plays a major role in the APT Low-Energy Linac (LEL) design. Engineering development is pushing ahead on several fronts, including thermal management, fabrication procedures, cavity and coupling slot tuning, high-power prototype fabrication and testing, supports and alignment, vacuum, and provisions for beam diagnostics. Fabrication of the CCDTL Low-Beta Hot Model is nearly complete, and high-power RF tests will commence soon. In 1999, the authors will begin the fabrication of 11 meters of CCDTL to be added to the Low-Energy Demonstration Accelerator. In 2001, it will take the 100 mA beam from 6.7 MeV to 10.05 MeV, producing the world`s most powerful proton beam. The authors are also starting the design of a CCDTL 96 MeV Hot Model to demonstrate cooling of an intermediate-Beta version of the structure. The 14cm-long, 9cm diameter drift tube has roughly 5kW dissipated on it. This all leads to the final mechanical design of the 113m long CCDTL for the APT plant linac.
Date: December 31, 1998
Creator: Wood, R.L.; Billen, J.H.; Hunter, W.T.; Leslie, P.O.; Roybal, R.J. & Sigler, F.E.
Partner: UNT Libraries Government Documents Department

New high power 200 MHz RF system for the LANSCE drift tube linac

Description: The Los Alamos Neutron Science Center (LANSCE) linac provides an 800 MeV direct H{sup +} proton beam, and injects H{sup {minus}} to the upgraded proton storage ring for charge accumulation for the Short Pulse Spallation Source. Accelerating these interlaced beams requires high average power from the 201.25 MHz drift tube linac (DTL) RF system. Three power amplifiers have operated at up to three Megawatts with 12% duty factor. The total number of electron power tubes in the RF amplifiers and their modulators has been reduced from fifty-two to twenty-four. The plant continues to utilize the original design of a tetrode driving a super power triode. Further increases in the linac duty factor are limited, in part, by the maximum dissipation ratings of the triodes. A description of the system modifications proposed to overcome these limitations includes new power amplifiers using low-level RF modulation for tank field control. The first high power Diacrode{reg_sign} is being delivered and a new amplifier cavity is being designed. With only eight power tubes, the new system will deliver both peak power and high duty factor, with lower mains power and cooling requirements. The remaining components needed for the new RF system will be discussed.
Date: December 31, 1998
Creator: Lyles, J.; Friedrichs, C. & Lynch, M.
Partner: UNT Libraries Government Documents Department

Smooth transverse and longitudinal focusing in high-intensity ion linacs

Description: We examine ion linac designs that start with a high energy radio- frequency quadrupole (RFQ) followed by either a drift-tube linac (DTL) or a coupled-cavity drift-tube linac (CCDTL). For high energies a conventional CCL follows the CCDTL. High RFQ output energy allows tailoring the transverse and longitudinal focusing strengths to match into the following structure. When the RFQ beam enters a higher frequency structure, the DTL or CCDTL starts with a low accelerating gradient and large negative synchronous phase. The gradient and phase both ramp up gradually to higher values. Other changes later in the machine are also gradual. Beam dynamics simulations show that these linacs require no separate matching sections. Applications include a cw 100 mA H{sup +} beam from a 350-MHz, 6.7 MeV RFQ injecting a 700 MHz CCDTL and CCL; a 7% duty 28 mA H{sup -} beam from a 402.5 MHz RFQ and DTL injecting 805 MHz structures; a cw 135 mA D{sup +} beam produced by a 175 MHz, 8 MeV RFQ and DTL; and a 2.4% duty, 80 mA H{sup +} beam using a 433 MHz 10 MeV RFQ and a 1300 MHz CCDTL. The machines take advantage of the considerable flexibility of the CCDTL. Designs can use a variety of different transverse focusing lattices. Use of two coupling cavity orientations permits a constant period even when the number of drift tubes per cavity changes along the linac.
Date: September 1, 1996
Creator: Billen, J.H.; Takeda, Harunori & Young, L.M.
Partner: UNT Libraries Government Documents Department

Modelling complex draft-tube flows using near-wall turbulence closures

Description: This paper presents a finite-volume method for simulating flows through complex hydroturbine draft-tube configurations using near-wall turbulence closures. The method employs the artificial-compressibility pressure-velocity coupling approach in conjunction with multigrid acceleration for fast convergence on very fine grids. Calculations are carried out for a draft tube with two downstream piers on a computational mesh consisting of 1.2x10{sup 6} nodes. Comparisons of the computed results with measurements demonstrate the ability of the method to capture most experimental trends with reasonable accuracy. Calculated three-dimensional particle traces reveal very complex flow features in the vicinity of the piers, including horse-shoe longitudinal vortices and and regions of flow reversal.
Date: December 31, 1996
Creator: Ventikos, Y.; Sotiropoulos, F. & Patel, V.C.
Partner: UNT Libraries Government Documents Department

Calculations of Operational and Residual Doses for the SNS Linac

Description: Dose profiles throughout the front-end building and the accelerator tunnel were calculated for the SNS linac system both for normal operation and after shut down of the facility based on normal operations beam losses. The calculated dose levels at an cylindrical envelope with 60 cm radius range from 0.08 to 10 rem/hr for the drift tube linac part, from 50-80 rem/hr for the coupled cavity linac part, from 1 to 20 rem/hr for the superconducting linac part, and from 70-200 rem/hr for the spare section extending after the linac. In the front-end building that houses the first 10 meters of the drift tube linac, dose levels of up to 500 mrem/hr were calculated that need to be reduced by adequate shielding, for example an ordinary concrete shield of up to 120 cm thickness. The shield thickness can be reduced by 25% using borated concrete or a layer of 20 cm borated polyethylene followed by ordinary concrete. The calculated residual dose levels in the accelerator tunnel are a factor of 2000-30 00 lower compared to the operational doses assuming a 30-year operations period and a 1hour decay period.
Date: August 13, 2001
Creator: Gallmeier, FX
Partner: UNT Libraries Government Documents Department


Description: Spallation Neutron Source (SNS) accelerator includes a nominally 1000 MeV, 2 mA average current linac consisting of a radio frequency quadrapole (RFQ), drift tube linac (DTL), coupled cavity linac (CCL), a medium and high beta super conducting (SC) linac, and two buncher cavities for beam transport to the ring. Los Alamos is responsible for the RF systems for all sections of the linac. The SNS linac is a pulsed proton linac and the RF system must support a 1 msec beam pulse at up to a 60 Hz repetition rate. The RFQ and DTL utilize seven, 2.5 MW klystrons and operate at 402.5 MHz. The CCL, SC, and buncher cavities operate at 805 MHz. Six, 5 MW klystrons are utilized for the CCL and buncher cavities while eighty-one 550 kW klystrons are used for the SC cavities. All of the RF hardware for the SNS linac is currently in production. This paper will present details of the RF system-level design as well as specific details of the SNS RF equipment. The design parameters will be discussed. One of the design challenges has been achieving a reasonable cost with the very large number of high-power klystrons. The approaches we used to reduce cost and the resulting design compromises will be discussed.
Date: June 1, 2001
Creator: REES, D.; LYNCH, M. & AL, ET
Partner: UNT Libraries Government Documents Department

Simulation of 10 A electron beam formation and collection for a high current EBIS

Description: Development of an Electron Beam Ion Source (EBIS) for the Relativistic Heavy Ion Collider (RHIC) at BNL requires operating with a 10 A electron beam, which is approximately an order of magnitude higher current than in any existing EBIS device. A test stand is presently being designed and constructed where EBIS components will be twisted. It will be reported in a separate paper at this Conference. The design of the 10 A electron gun, drift tubes and electron collector requires extensive computer simulations. Calculations have been performed at Novosibirsk and BNL using two different programs, SAM and EGUN. Results of these simulations will be presented.
Date: November 1, 1997
Creator: Kponou, A.; Beebe, E.; Pikin, A.; Kuznetsov, G.; Batazova, M. & Tiunov, M.
Partner: UNT Libraries Government Documents Department

Resonance Control Cooling System for the APT/LEDA CCDTL Hot Model

Description: The Hot Model for the Coupled Cavity Drift Tube Linac (CCDTL) resonance control cooling system (RCCS) for the Low Energy Demonstration Accelerator (LEDA) [1] in support of the Accelerator Production of Tritium (APT) [2] is described. Two hydraulic control loops are described that control the frequency in the CCDTL Hot Model cavity. The two loops supply the required flow to the 32 channels. Control system schema is described to regulate resonant frequency during steady state operation.
Date: April 8, 1999
Creator: Domer, G.; Floersch, R. & Jett, N.
Partner: UNT Libraries Government Documents Department

A compact high-power proton linac for radioisotope production

Description: Conventional designs for proton linacs use a radiofrequency quadrupole (RFQ), followed by a drift-tube linac (DTL). For higher final beam energies, a coupled cavity linac (CCL) follows the DTL. A new structure, the coupled-cavity drift-tube linac (CCDTL) combines features of an Alvarez DTL and the CCL. Operating in a {pi}/2 structure mode, the CCDTL replaces the DTL and part of the CCL for particle velocities in the range 0.1 < {beta} < 0.5. The authors present a design concept for a compact linac using only an RFQ and a CCDTL. This machine delivers a few mA of average beam current at a nominal energy of 70 MeV and is well suited for radioisotope production.
Date: May 1, 1995
Creator: Takeda, H.; Billen, J.H.; Nath, S.; Stovall, J.E.; Wood, R.L. & Young, L.M.
Partner: UNT Libraries Government Documents Department