Review of Charged Particle Dynamics. Beam Optics and Focusing Systems Without Space Charge. Linear Beam Optics with Space Charge. Self-Consistent Theory of Beams. Emittance Variation. Beam Physics Research from 1993 to 2007. Appendices. List of Frequently Used Symbols. Bibliography. Index.

Theory and Design of Charged Particle Beams

A 20 MeV, 30 mA CW proton linac is being developed at BARC, Mumbai. This linac will consist of an ECR ion source followed by a Radio Frequency Quadrupole (RFQ) and Drift tube Linac (DTL). The low energy beam transport (LEBT) line is used to match the beam from the ion source to the RFQ with minimum beam loss and increase in emittance. The LEBT is also used to eliminate the unwanted ions like H2+ and H3+ from entering the RFQ. In addition, space charge compensation is required for transportation of such high beam currents. All this requires careful design and optimization. Detailed beam dynamics simulations have been done to optimize the design of the LEBT using the Particle-in-cell code TRACEWIN. We find that with careful optimization it is possible to transport a 30 mA CW proton beam through the LEBT with 100% transmission and minimal emittance blow up, while at the same time suppressing unwanted species H2+ and H3+ to less than 3.3% of the total beam current.

http://iopscience.iop.org/article/10.1088/1748-0221/10/02/P02001/pdf

Optimization of solenoid based low energy beam transport line for high current H+ beams

Physics and technology for development of accelerator driven systems in India

The Low Energy High Intensity Proton Accelerator (LEHIPA), being developed at the Bhabha Atomic Research Centre (BARC) will produce a 20 MeV, 30 mA, continuous wave (CW) proton beam. At these low velocities, space-charge forces dominate, and could lead to larger beam sizes and beam halos. Hence in the design of the focusing lattice of the LEHIPA drift tube linac (DTL) using permanent magnet quadrupoles (PMQs), a larger good field region is preferred. Here we study, using the two dimensional (2D) and three dimensional (3D) simulation codes PANDIRA and RADIA, four different types of cylindrical PMQ designs: 16-segment trapezoidal Halbach configuration, bullet-nosed geometry and 8- and 16-segment rectangular geometries. The trapezoidal Halbach geometry is used in a variety of accelerators since it provides very high field gradients in small bores, while the bullet-nosed geometry, which is a combination of the trapezoidal and rectangular designs, is used in some DTLs. This study shows that a larger good field region is possible in the 16-segment rectangular design as compared to the Halbach and bullet-nosed designs, making it more attractive for high-intensity proton linacs. An improvement in good-field region by ∼16% over the Halbach design is obtained in the optimized 16-segment rectangular design, although the field gradient is lower by ∼20%. Tolerance studies show that the rectangular segment PMQ design is substantially less sensitive to the easy axis orientation errors and hence will be a better choice for DTLs.

An improved permanent magnet quadrupole design with larger good field region for high intensity proton linacs

Bhabha Atomic Research Centre, Trombay is developing LEHIPA (Low Energy High Intensity Proton Accelerator) as pre-injector for 1 GeV proton accelerator for proposed ADSS (Accelerator Driven Sub-critical reactor System). LEHIPA is 20 MeV, 30 mA room temperature accelerator and consists of RFQ (Radio Frequency Quadrupole) and DTL (Drift Tube Linac) as major accelerating structures. The RF (Radio Frequency) design of DT (Drift Tube) of DTL aimed at maximizing the shunt impedance; this demands the size (transverse) of DTs to be minimal. The width of the DT is governed by the β of the particle and trade-off between transit time factor and effective accelerating voltage in the DT gap. The availability of limited volume in DTs for housing magnetic quadrupole has motivated the use of permanent magnets for generating the quadrupole field, as they have high magnetic energy density when compared to conventional electromagnets. With usage of permanent magnets, joule heating is eliminated, this helps in limiting the heat load. DTL has copious microwave heat with heat flux as large as 10 W/cm2 at certain locations. The beam dynamics requires uniformity of integral magnetic field gradient of PMQ (Permanent Magnet Quadrupole) to be better than ± 0.5% with nominal value of 2.05 T. Further the drift tubes which houses these PMQs have microwave heat generation on outer surface which ranges from 5 kW to 8 kW depending on the size of the DT. This heat is required to be removed, not doing so would result in resonant frequency detuning in DTL cavity and enhanced temperature would deteriorate the strength of permanent magnets of the PMQ, thereby compromising their focal length. The drift tube has hydraulic circuit for microwave heat removal. This paper describes the magnetic design of the PMQ using Sm2Co17 rare earth permanent magnets. Paper discusses the magnetic design for optimizing integral magnetic field gradient (integral Gdl) uniformity. A novel magnetic field tuning technique is used for tuning the integral magnetic field gradient to required value. Comprehensive magnetic tuning and characterization scheme is presented which relates the measured magnetic moment of the permanent magnets, un-tuned integral Gdl and pole length to the required integral Gdl. Based on this scheme thirty six PMQ embedded drift tubes have been developed. Paper also details the results of characterization of twenty PMQs which forms part of 10 MeV to 15 MeV DTL. The scheme used for tuning integral magnetic field gradient is universal and can be implemented in similar permanent magnets quadrupoles and other permanent magnet based systems.

Design, development and characterization of tunable Permanent Magnet Quadrupole for Drift Tube Linac

The response of the liquid scintillator (EJ-301 equivalent to NE-213) to the monoenergetic electrons produced in Compton scattered $\gamma$-ray tagging has been carried out for various radioactive $\gamma$-ray sources The measured electron response is found to be linear up to $\sim$4~MeVee and the resolution of the liquid scintillator at 1~MeVee is observed to be $\sim$~11\% The pulse shape discrimination and pulse height response of the liquid scintillator for neutrons has been measured using $^7$Li(p,n$_1$)$^7$Be*(0429 MeV) reaction Non linear response to mono-energetic neutrons for the liquid scintillator is observed at E$_n$=53, 90 and 127 MeV The measured response of the liquid scintillator for electrons and neutrons have been compared with Geant4 simulation

Measurement of the response of a liquid scintillation detector to monoenergetic electrons and neutrons

The response of a liquid scintillator (EJ-301) to monoenergetic electrons tagged by Compton back scattered γ-rays has been measured using various radioactive γ-ray sources. It is observed that the measured electron response is linear up to an energy of ∼4 MeV. The resolution of the liquid scintillator at an energy 1 MeVee is found to be ∼ 11%. The pulse shape discrimination and pulse height response of the liquid scintillator for neutrons have been measured using the 7Li(p,n1)7Be*(0.429 MeV) reaction. A nonlinear response to mono-energetic neutrons for the liquid scintillator is observed at energies En=5.3 MeV, 9.0 MeV and 12.7 MeV. In addition, the measured response of the liquid scintillator for electrons and neutrons has been compared with simulated results obtained using the Monte Carlo based Geant4 toolkit.

Measured response of a liquid scintillation detector to quasi-monoenergetic electrons and neutrons

A 20 MeV, 30 mA CW proton accelerator is being built in BARC which consists of 50 keV ECR ion-source, LEBT, 3 MeV RFQ, MEBT and 20 MeV DTL. In designing low energy beam transport (LEBT) line, which matches the beam from ion-source to RFQ, the expansion of the proton beam is a severe problem. As the energy of the beam is 50 keV, Coulomb repulsion is enormous and for minimization of this repulsion, space charge compensation is done. To simulate the beam dynamics part, a PIC code is written, which allows beam of different distributions like KV, Parabolic and Waterbag. This is an electrostatic code, which can also take care of external magnetic fields. A Monte Carlo collision scheme is being implemented for the ionization of the background gas. In this paper, we are presenting the simulation of space charge compensation of the 30 mA proton beam at 50 keV.

/pdf/study-of-space-charge-compensation-in-lebt-44qf120nhs.pdf

Study of space charge compensation in lebt

High-power proton linacs have various applications such as Accelerator Driven Systems (ADS) for transmutation or energy production, neutron spallation source for condensed matter studies, neutrino factories and muon colliders, production of rare isotope beams for nuclear physics studies, etc. These linear accelerators are required to deliver proton beams of up to several MW to several tens of MW power and operate with CW or pulsed high intensity beams. In particular, Accelerator Driven Systems (ADS) [1] have evoked considerable interest in the nuclear community the world over because of their capability to incinerate the MAs (minor actinides) and LLFPs (Long-lived Fission Products) radiotoxic waste and utilization of Thorium as an alternative nuclear fuel. Since India has vast resources of Thorium, ADS is particularly important as one of the potential routes for accelerated thorium utilization [2]. An ADS consists of a sub-critical reactor coupled to a high power proton accelerator through spallation target as shown in Fig. 1. The linac for an Accelerator Driven System is required to deliver a 1 GeV proton beam at

BEAM DYNAMICS FOR THE 1 GeV PROTON LINAC FOR ADS

At BARC, development of a Low Energy High Intensity Proton Accelerator (LEHIPA), as front-end injector of the 1 GeV accelerator for the ADS programme, has been initiated. The major components of LEHIPA (20 MeV, 30 mA) are a 50 keV ECR ion source, a 3 MeV Radio Frequency Quadrupole (RFQ) and a 20 meV drift tube linac (DTL). The Low Energy Beam Transport (LEBT) and Medium Energy Beam Transport (MEBT) lines match the beam from the ion source to RFQ and from RFQ to DTL respectively. Design of these systems has been completed and fabrication of their prototypes has started. Physics studies of the 20–1000 MeV part of the Linac are also in progress. In this paper, the present status of this project is presented.

Accelerator development in India for ADS programme

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