G. Stanford

Radioactive ion beams facility at TRIUMF

Abstract A radioactive ion beam (RIB) facility is being built at TRIUMF. A novel design for the target/ion source station will allow us to bombard a thick target with TRIUMFs 100 μA, 500 MeV proton bam, producing a variety of very intense beams of nuclei far from stability. After mass separation the beams can be sent to two different experimental areas. One uses the 60 keV energy beam and the second one will use the 0.15 to 1.50 MeV/u post-accelerated beam. Singly charged ion beams, with A ≤ 30 delivered from the on line mass separator, with an energy of 2 keV/u, will be accelerated in a two stage linac consisting of an RFQ and a post-stripper drift-tube linac up to 1.5 MeV/u. CW operation mode is required to preserve beam intensity. As a consequence of the low q/A ions a low operating frequency for the RFQ is required to achieve adequate transverse focusing. The main features of this accelerator are: 35 MHz RFQ, stripping at 150 keV/u, beam energy continuously variable from 0.15 to 1.50 MeV/u and CW operation.

The ISAC-II upgrade at TRIUMF - progress and developments

TRIUMF is proceeding with a major upgrade to the ISAC project, ISAC-II, that includes the addition of 43 MV of heavy ion superconducting linear accelerator and an ECR charge state booster. An initial installation of 18 MV of mid beta cavities (/spl beta/ = 5.8%, 7.1%) is due for commissioning in 2005. The paper will describe the superconducting linac program at TRIUMF including the status of the production cavities, the design of the medium beta cryomodule and a summary of the activities of the SCRF laboratory.

Commissioning the TRIUMF/ISAC electron cyclotron resonance ion source for radioactive ion beams

A radiation hard 2.45 GHz ECR source has been installed in the ISAC target station. The ion source with its 8–60 kV extraction system is coupled to the radioactive isotope production target via a short transfer tube. The volatile radioactive isotopes produced by bombarding a target with a 500 MeV proton beam, are ionized and accelerated at the ECR source system. The source is reengineered to withstand a dose rate of 105 Gy/h from the activation of the target by the 500 MeV, 100 mA proton beam. The whole assembly is located beneath a 2 m thick steel shielding structure. Design aspect of the source and the initial results obtained during the commissioning at the ISAC terminal, as well as preliminary results obtained at the test stand are presented.

Design of the Medium‐Beta Cryomodule for the ISAC‐II Superconducting Heavy Ion Accelerator

ISAC‐II is an upgrade of the ISAC radioactive beam facility that includes the addition of 43 MV of heavy ion superconducting accelerator. The initial milestone in achieving this goal is the design and manufacture of a prototype medium‐beta cryomodule scheduled for completion late in 2003. A medium‐beta cryomodule comprises four superconducting cavities and one superconducting solenoid magnet. The cryomodule has an inventory of 190 liters of liquid helium at 4.5‐K under constant replenishment from the refrigeration system during normal operating conditions. This paper will describe the design and engineering of the medium‐beta cryomodule including the internal mechanical design and layout, LN2 shielding, alignment method and expected thermal loads.

Tank1 of the ISAC-DTL LINAC

The first phase of the ISAC radioactive ion beam facility at TRIUMF is now completed. It combines an isotope separator-on-line with a post accelerator. In the second phase a drift-tube LINAC is required to accelerate ions with a charge to mass ratio /spl ges/1/6 from E=0.15 MeV/u to a final energy fully variable up to 1.5 MeV/u. Due to the relatively low intensities of some of the radioactive ion species continuous (cw) operation of the accelerator is preferred. An interdigital H type RF structure is chosen because of its very high shunt impedance. The ISAC-DTL is composed of five IH tanks and three rebunchers, operating at 105 MHz. The basic design of the structure is similar to other IH structures with the exception that the stems are water-cooled. The features of this mechanical design will be discussed and the first results of the RF tests are presented.

RECENT OPERATING EXPERIENCE FOR THE ISAC-II SC-LINAC CRYOGENIC SYSTEM AT TRIUMF

A first stage of the heavy ion superconducting linac cryogenic system comprising a 500 W liquid helium refrigerator and distribution system has been installed and is now operational at TRIUMF. The recent operational experience with the cryogenic systems, including thermal loads data, and refrigerator performance, will be presented.

Status of the ISAC‐II Cryogenic System

ISAC‐II is an upgrade of the radioactive‐beam facility that includes the addition of a 48‐MV heavy‐ion superconducting linear accelerator (LINAC). A first stage comprising a 500 W class LHe refrigerator and distribution piping to five cryomodules is scheduled for commissioning and operation in the fall of 2005. The paper will present the design, installation and commissioning of the phase 1 system, including a description of the refrigerator, helium storage, gas recovery, distribution piping and overall refrigerator / LINAC layout.

First Cold Test of the ISAC-II Medium Beta Cryomodule

Publisher Summary This chapter summarizes the design of a medium-beta cryomodule and presents the results of the first cold test and alignment. A medium-beta cryomodule comprises four superconducting quarter-wave cavities and one superconducting solenoid magnet. An initial cryomodule has been assembled and cooled with LHe from a supply dewar. Each cryomodule has a single vacuum system for thermo-isolation and beam. This demands extreme cleanliness of internal components to avoid superconducting surface contamination. The first medium beta cryomodule cold test has been a total success. The distribution “spider” distributes the cold gas evenly to the bottom of the cold mass. The static load and required LN2 flow are 10W and 5ltr/hr respectively, within design estimates. A WPM six monitor system developed at TRIUMF is now operational. The system monitors continuously the position of the structure during cold cycling. The three point mount system produces a slight temperature dependent skew in the cavity support frame.

Cold Tests of the ISAC‐II Medium Beta Cryomodule

ISAC‐II is an upgrade of the ISAC radioactive‐beam facility that includes the addition of a ∼ 40 MV heavy‐ion superconducting accelerator. This accelerator consists of five medium‐beta cryomodules. Each cryomodule is comprised of four superconducting quarter‐wave cavities and one superconducting solenoid magnet. The cryomodule has an inventory of 190 liters of liquid helium at 4.5 K that is constantly replenished from the refrigeration system during normal operating conditions. The first cryomodule has been assembled and fully characterized during the cold tests, including a cool down with ISAC‐II LINDE helium refrigerator in the final SC‐linac location. The beam injected from ISAC‐I was successfully accelerated with the cryomodule. This confirmed the validity of the overall design. Also, the second cryomodule was cooled down with cryogenic performance similar to the first cryomodule. The results of the cold tests are presented.

A radiation hard ECR source for ISAC

The design of a radiation hard ECR source for the ISAC radioactive beam facility has been completed. The ion source with its 0–60 kV extraction system is coupled to the radioactive isotope production target via a small transfer tube. For a typical ISAC target the copper coils of the ECR source will be exposed to a dose rate of about 105 Gy/h for a 100 μA∼500 MeV incident proton beam. The whole assembly is located beneath a 2 m thick steel shielding structure. Construction details of the target-ion source system and auxiliary equipment are described. The source will be tested at the TRIUMF test bench during the second half of 2001 and will be installed in the ISAC facility by the middle of 2002.