The efficiency of trapping ions in an electron-beam ion source (EBIS) is of primary importance for many applications requiring operations with externally produced ions: RIA breeders, ion sources, and traps. At the present time, the most popular method of ion injection is pulsed injection, when short bunches of ions get trapped in a longitudinal trap while traversing the trap region. Continuous trapping is a challenge for EBIS devices because mechanisms which reduce the longitudinal ion energy per charge in a trap (cooling with residual gas, energy exchange with other ions, and ionization) are not very effective, and accumulation of ions is slow. A possible approach to increase trapping efficiency is to slant the mirror at the end of the trap which is opposite to the injection end. A slanted mirror will convert longitudinal motion of ions into transverse motion, and, by reducing their longitudinal velocity, prevent these ions from escaping the trap on their way out. The trade-off for the increased trapping efficiency this way is an increase in the initial transverse energy of the accumulated ions. The slanted mirror can be realized if the ends of two adjacent electrodes, drift tubes, which act as an electrostatic mirror, are machined to produce a slanted gap, rather than an upright one. Applying different voltages to these electrodes will produce a slanted mirror. The results of two-dimensional (2D) and three-dimensional (3D) computer simulations of the ion injection into an EBIS are presented using simplified models of an EBIS with conical (2D simulations) and slanted (3D simulations) mirror electrodes.

In order to provide a variety of ion species to the BNL relativistic heavy ion collider (RHIC) and NASA Space Radiation Laboratory facilities on a pulse-to-pulse basis, the BNL RHIC electron beam ion source (EBIS) will use injection of primary “seed” ions from external low charged ion sources. As part of the prototype for the RHIC EBIS low energy beam transport line, a switchyard for seed ion injection and extracted EBIS ion beams has been constructed. The ion injection line includes a hollow cathode ion source (HCIS), four quadrupole lenses, a switchyard, gridded lenses, and other deflection optics. The HCIS is based on one obtained from CEA Saclay [B. Visentin et al., Phys. Scr., T 71, 204 (1997).] and has been used in bench studies in the production of low charged metal and gas ions, as well as in BNL test EBIS injection studies for the production of highly charged ions. The HCIS geometry and extraction optics have been modified to be able to reach the output currents necessary to seed the test EBIS. Ion currents greater than 60μA Cu+ and 130μA Ne+ have been extracted from the modified HCIS at 12–15kV and plasma aperture of 1–1.5mm. The HCIS discharge is initiated by a rf coil and can be operated stably at pulse rates from 1to100Hz. Measurement of the emittance of injector beam before and after the injection switchyard will be provided, as well as results from ion injection into the test EBIS using the new injector configuration.

At BNL, we are preparing to build an electron beam ion source (EBIS) that will satisfy the requirements of the relativistic heavy ion collider (RHIC), e.g., Au32+ ions of about 3×109 particles/pulse in 10–40μs pulses at 5Hz. In addition, the EBIS is required to deliver beams such as He2+, C6+, O8+, Si14+, Ti18+, Fe21+, and Cu22+ in ∼2–3mA, 10μs pulses at 5Hz to meet the demands of the NASA Space Radiation Laboratory (NSRL) experimental program. Development studies continue to be carried out on the BNL test EBIS, a half-length full electron beam power prototype of the RHIC EBIS which is in the construction phase. In preparation for acceleration of EBIS ions by a radio frequency quadrupole, we have upgraded the test EBIS for operation on a nominal 100kV pulsed platform to allow seed ion injection at 10–20kV and ion extraction up to 100qkV. The installation includes a pulsed high voltage power supply, a 200kVA 100kV isolation transformer, and a capacitive electron collector supply and electron gun bias supply which allows operation in a similar mode to the RHIC EBIS design. Initial testing has been made using ion beams of He2+ and Ar10+ formed from gas injection and ions have been extracted with energies up to 88qkeV. Total ion current measurement has been made and charge state distributions have been obtained using a Mamyrin time of flight. Results of emittance measurements and profile distributions, obtained at various energies using both pepperpot and slit-foil emittance meters, will be presented.

Methods of producing the nuclear polarized He-3(+) ions and their ionization to He-3(+) in ion trap of the electron Beam Ion Source (EBIS) are discussed. Computer simulations show that injection and accumulation of He-3(+) ions in the EBIS trap with slanted electrostatic mirror can be very effective for injection times longer than the ion traversal time through the trap.

A liquid metal ion source (LMIS) has several attractive features as an external injector of primary ions (mostly metallic ions) into electron-beam ion source (EBIS). It does not use a buffer gas and therefore it provides only a very small gas load to the system; its control and operation are simple, power consumption does not exceed 10W, and beam pulses are very stable. A gold-silicon LMIS was supplied by FEI Company (http://www.feibeamtech.com/pages/liquid.html) and tested in a pulsed regime with an ion pulse width of 2ms and frequency up to 5Hz. Total extracted ion current reached 50μA and the normalized emittance of the total ion beam was 0.05πmmmrad. The results of this test, as well as results of experiments in which this ion source is used for injection of Au ions into EBIS, are presented.

The maximum achievable perveance of the electron beam in the ion trap region and in the electron collector of the BNL Test electron-beam ion source (EBIS) has been measured for different electron-beam currents. These perveances determine the maximum degree of electron-beam retardation in these areas, which limits for the first case the maximum capacity of the ion trap, and for the second case the minimum dissipated power on the electron collector, for a given electron current. The results are compared with the results of optical simulations of the electron beam. In another set of experiments, data on Test EBIS ionization efficiency for different experimental conditions were obtained. These results are presented and compared with calculations based on stepwise ionization assuming 100% ion confinement in the trap. Finally, a series of experimentally measured longitudinal-energy spectra of the extracted ion beam are presented, and will be compared with the calculated energy spread.

Following the successful development of the Test EBIS at BNL [1-3], we now have a design for an EBIS-based heavy ion preinjector which would serve as an alternative to the Tandem Van de Graaffs in providing beams for RHIC and the NASA Space Radiation Laboratory. This baseline design includes an EBIS producing mA-level currents of heavy ions (ex. Au 32+ ) in ∼ 10-20 μs pulses, injecting into an RFQ which accelerates the beams to 300 keV/amu, followed by an IH linac accelerating to 2 MeV/amu. Some details of this design are presented, as well as recent experimental results on the Test EBIS.

Successful operation of the BNL EBIS with electron current up to 10 A provides optimism that EBIS operation with even higher electron current should be possible. We are now considering key aspects of the design for an EBIS operating with electron current 20 A. Several technical problems need to be resolved, including generation of a 20 A electron beam and dissipation of this electron beam power on the electron collector. Since we already have a tested concept of electron beam generation with the gun immersed in a magnetic field and subsequent purely magnetic compression of the electron beam, it makes sense to develop the new electron gun with immersed cathode but with higher perveance. To distribute the electron beam power on the surface of the electron collector more evenly, the emission current density from the cathode can be made bell-shaped with minimum close to zero on the periphery of the electron beam. With the already high requirements to the emission current density, and since such shaping of the electron beam makes these requirements even higher, perhaps the only available cathode material that can satisfy these requirements is IrCe. The problems of power dissipation on the electron collector (EC) include heat removal with cooling water and fatigue of the EC material. The first step in the EC design was electron beam transmission simulation with the goal to reduce `spikes' of power density on EC surface as much as possible. With the geometry of EC thus defined, the conditions of heat exchange for several modes of EBIS operation have been analyzed and cooling parameters, which provide adequate heat removal were found. The last step was stress analysis of several EC materials with ANSYS to find the material suitable for this application. Details of the 20 A electron gun and collector are presented.

Based on the successful experience of the Brookhaven National Laboratory test electron beam ion sources (EBIS), the relativistic heavy ion collider (RHIC) EBIS design utilizes a 10 A electron beam to produce the required ion source output intensity of 3.4×109 of Au32+ ions per 10–40 μs pulse. In order to provide increased cathode lifetime and reliability at the required 10 A, and accommodate future upgrades of RHIC EBIS ion intensity, it is desirable to upgrade the electron gun. Simulations have been made for a new electron gun and electron collector capable of generating and dissipating an electron beam with current up to 20 A. The method of forming the electron beam using magnetic compression and inverse magnetron geometry of the electron gun are the same as has been tested successfully on the electron beam test stand. The new gun has higher perveance and partially shielded spherical cathode. A bell-shaped radial current density distribution with reduced current density on a periphery of the beam, combined with a modified shape of the electron collector magnet shim, yields a simulated power density on the surface of the electron collector below 400 W/cm2 for electron beam currents up to 20 A.

Most design goals of the BNL Test EBIS Project have been exceeded and we are confident that an EBIS meeting RHIC requirements can be built. Achieved parameters include 10 A electron beam current, ion charge state above Au32+, and greater than 55 nC total extracted ion charge. The Test EBIS utilizes the full electron beam power but has only half the trap length and operates at a reduced duty factor compared with an EBIS for RHIC, which would produce at least 85 nC total ion charge in 10–40 microsecond pulses, containing ~3 × 109 particles/pulse of Au32+ ions. Normalized rms emittance values for 1–3 mA extracted ion beams have been in the range of 0.08–0.1 pi mm mrad. Present development of the source is focused on establishing operational reliability and facilitating future upgrades in ion intensity and species, since the major emphasis is now on integrating the EBIS into a pre-injector facility, including an RFQ and linac. Recent progress towards this goal includes the following: (1) An IrCe electron gun cathode and modified anode have been installed in an electron gun chamber separable from the source ionization region by a gate valve. A very low loss 10 A, electron beam has been propagated with the new configuration, with 100 kW peak power dissipation at the electron collector. (2) A new electron collector power supply configuration has been tested which can lower the cost compared to our present setup, while improving the stability of the electron beam launch. This is an important first step towards placing the EBIS on a nominal 50 kV platform, necessary for efficient highly charged ion transport to the RFQ. (3) A hollow cathode ion source obtained from CEA Saclay, has been tested and is being installed. This will allow us to provide a variety of ion species to the RHIC and NASA Space Radiation Laboratory facilities, and is valuable at the present project stage for beamline development and emittance studies of heavy and light ion beams of highly charged ions from the EBIS. (4) An electron collector for RHIC has been designed which would allow operation exceeding 10 A electron beams at 100% duty factor. The RHIC collector design could allow upgrades to 300 kW electron beam power. (5) Controls for pulse to pulse switching and diagnostics for charge state and charge fraction verification have been developed.

An electron beam ion source (EBIS) that would satisfy Relativistic Heavy Ion Collider (at Brookhaven National Laboratory) (RHIC) requirements should be capable of producing intensities of, e.g., Au32+ ions of about 3×109 particles/pulse in 10–40 μs pulses. The total charge extracted (all charge states) would be 85 nC, assuming 20% in the peak charge state. To achieve this at Brookhaven National Laboratory, pulsed-electron beam currents up to 10 A, 100 ms are being used. A test EBIS has been constructed, designed for the full electron beam power and having close to half of the trap length of an EBIS for RHIC. As a result of successful experiments on the test EBIS, we are confident that an EBIS meeting RHIC requirements can be built. Initial electron beam tests have demonstrated a 100 ms, 8.6 A electron beam through the EBIS trap. The stable operation of 10 A, 50 ms electron beams through the EBIS trap has also been achieved. Gold spectra with a dominant charge state 34+ and total ion charge 55 nC measured on a current transformer have been obtained at the EBIS exit after a 30 ms confinement period. Recent studies with an in-line time-of-flight spectrometer with measurement of charge on a Faraday cup have shown 83% of the >28 nC extracted charge to be Au ions peaked at Au25+, for a 7 A electron beam and 10 ms confinement period. Typical normalized rms emittance values using a 6.8 A electron beam, 20–40 nC total ion charge, and 1–3 mA extracted ion current have been in the range of 0.08–0.1 π mm mrad. An energy analysis of the total extracted ion pulses >35 nC has indicated a longitudinal energy spread of <2 kV full width at half maximum after a 35 ms confinement period using a 7 A electron beam. Most design goals have been exceeded and much of the present work is geared toward improving reliability and providing larger safety margins. These include upgrading the electron gun, decoupling the electron beam launch energy from the electron collection energy, and tailoring the magnetic fields to reduce electron beam losses. Details of these measurements, tests in progress to improve performance, and plans for optimizing the design of the RHIC EBIS will be presented.

An Electron Beam Ion Source (EBIS) can be used to produce beams of high charge state heavy ions, and is an excellent choice for injection into a synchrotron, since short pulses of high intensity can be produced for single-or few-turn injection into the ring. As a result of successful experiments on a test EBIS at BNL, we are now confident that an EBIS meeting RHIC requirements can be built. This EBIS would be part of a new linac-based preinjector which would serve as a modem alternative to the existing Tandem preinjectors, offering improvements in performance and operational simplicity. The BNL test EBIS, which is a 1/2 trap-length prototype of the RHIC EBIS, has produced > 10(9) ions per pulse of Au32+ in 10-20 microsecond pulses, and has exceeded our design goals. Performance of the test EBIS is summarized and the design of the RHIC EBIS presented.

The BNL EBIS Test Stand (EBTS), is a full electron beam power, half ion trap length prototype for an Electron Beam Ion Source (EBIS) that could meet requirements for the Relativistic Heavy Ion Collider (RHIC) preinjector. (1). The EBTS uses a 10 A, ~50 ms pulsed electron beam to produce intense pulses of highly charged ions, of ~55 nC total positive charge yield and as short as 10 µs duration. An auxiliary ion source is used to inject primary low charged Au ions into the EBTS in ~500 µs pulses. The EBIS controller handles all the digital timing and many analog control signals used for power supply and device control necessary, for stable, low loss EBIS operation. Diagnostics used to monitor the electron and ion beams include Faraday cups, current transformers, a Mamyrin TOF for providing high resolution ion spectra for highly charged heavy ions (e.g., Au34+) at 20 kV extraction energy, harp-type beam profile monitors and a compact emittance head. The design and operation of these devices will be discussed.

Excellent progress has been made in the operation of the Brookhaven National Laboratory electron beam ion source (EBIS), which is a prototype for an EBIS that could meet requirements for a RHIC preinjector. We have achieved very stable operation of the electron beam at 10 A through the EBIS trap. Ion injection of low charge gold ions from a low energy vacuum ion source [Brown et al., Rev. Sci. Instrum. 65, 1260 (1994)] and subsequent extraction of these ions with most probable charge state Au34+ has been demonstrated with electron beams up to 8 A. The total ion charge for gold measured on current transformer at the EBIS exit was 55 nC after a 30 ms confinement period. This corresponds to ∼85% of the theoretical ion trap capacity and exceeds our goal of 50% neutralization. The collected ion charge is proportional to the electron current and the gold charge state scales with the electron current density. Details of the EBIS configuration, total charge measurements, and time-of-flight spectra are given.

All design goals of the original proposal [1,2] have been reached in the operation of the BNL Electron Beam Ion Source (EBIS), which is a prototype for an EBIS that could meet requirements for a RHIC preinjector. RHIC requires 3.4x10 ions Au per pulse, or about 85 nC total positive charge yield, assuming a 20 % abundance of the selected charge state. Stable operation of a 10 A, 50 ms electron beam through the EBIS trap has been achieved. Ion injection of low charge gold ions from a low energy vacuum arc ion source (LEVA) [3] and subsequent extraction of high charge state Au has been demonstrated with electron beams up to 8A. Gold spectra with dominant charge state 34+ and total ion charge of 55 nC measured on a current transformer at the EBIS exit has been obtained after a 30 ms confinement period. This corresponds to ~85% of the theoretical ion trap capacity, and exceeds our goal of 50% neutralization. Time-offlight spectra indicate that 20% of the gold charge is concentrated in charge state 34+. The collected ion charge is proportional to the electron current and the gold charge state scales with the electron current density.

Experiments on the Brookhaven National Laboratory EBIS electron beam test stand (EBTS) with the ion trap extending beyond the edges of the superconducting solenoid had the main goal to study ion trap operation with a trap length exceeding that of the normal EBTS trap. Preliminary results indicate that the ion trap with a length of 107 cm is stable and controllable in the same fashion as our normal 70 cm trap with a multiampere electron beam. EBTS operation with ion trap 145 cm long and with electron current up to 3 A in earlier experiments also was stable and yielded more ions than from the basic “short” trap. These results increased our confidence in operation of the proposed RHIC in a stable mode and in the correctness of linear scaling of ion intensity with the length of the ion trap.

Work is continuing on the development of an Electron Beam Ion Source (EBIS) which could be used as part of a new heavy ion injector for RHIC. On a test EBIS, we have operated with an electron beam current of up to 1.14 A, and have extracted ions such as Tl/sup 41+/, Xe/sup 26+/, Ar/sup 14+/, N/sup 7+/, and Na/sup 7+/. Recent experimental results are reported. In addition, we discuss plans for a new electron beam test stand that is now being built. This will allow operation with electron currents of 10 A, as well as testing of a warm-bore superconducting magnet system, methods for fast extraction of ions, and possible off-axis collection of the electron beam.

A proposed new heavy ion preinjector for RHIC is described. The progress made at BNL on the development of an Electron Beam Ion Source (EBIS) has increased our confidence that one can build a preinjector meeting RHIC requirements using an EBIS producing intermediate charge state heavy ions. A new RFQ and Linac will be required to accelerate beams from this source to an energy sufficient for injection into the AGS Booster. These are both straightforward devices, very similar to ones already in operation at other laboratories. Injection into the Booster will occur at the same location as the existing heavy ion injection from the Tandem Van de Graaff.

Experimental study of the BNL Electron Beam Test Stand (EBTS), which is a prototype of the Relativistic Heavy Ion Collider (RHIC) Electron Beam Ion Source (EBIS), is currently underway. The basic physics and engineering aspects of a high current EBIS implemented in EBTS are outlined and construction of its main systems is presented. Efficient transmission of a 10 A electron beam through die ion trap has been achieved. Experimental results on generation of multiply charged ions with both continuous gas and external ion injection confirm stable operation of the ion trap.