HIE-ISOLDE Project Research Articles

Measurement of RF characteristics for Superconducting Quarter-wave Resonator

RF characteristics of unloaded quality factor (Q0) and accelerating electric field (Eacc) were measured for superconducting quarter-wave resonator (QWR) in order to verify the performance. For the accurate measurement of RF characteristics, the measurement method of Q0 based RF power and RF coupling coefficient was used, and the measurement uncertainty was calculated with statistics analysis of systematic error in RF measurement system. The superconducting QWR was designed with a resonant frequency of 101.28 MHz and an accelerating electric field (Eacc) of 6 MV/m at a cavity dissipation power of 10 W in the high-intensity and energy isotope separator online device (HIE-ISOLDE) project at CERN. Q-slopes and RF coupling coefficients were measured for three QWRs at the resonant frequency 101.28 MHz. Q0 values of QWRs were measured 4.55 × 108, 3.78 × 108 and 3.17 × 108 at the 6 MV/m, respectively, and the measurement uncertainty of Q0 and Eacc were calculated 2.92% and 3.32%. Performances of superconducting QWRs were acceptable to operate the beam acceleration with consideration of cryomodule capacity in HIEISOLDE project.

Design of a single magnet separator with mass resolving power [formula omitted

ISOLDE at CERN is a leading radioactive ion beam facility. With its upgrade, the HIE-ISOLDE project, an increase in primary beam intensity and energy is envisaged and the aim is a significant increase in intensity of the exotic beams. The high resolution separator (HRS) after the upgrade is required to suppress contaminations almost completely when the masses differ to the beam of interest by Δm/m>1/20,000. Here a 120° magnet with a bending radius of 1.25m has been chosen. The magnetic rigidity is 0.625Tm (B-field of 0.5T) to allow for separation of molecules of up to a mass of 300u. The magnet comprises a yoke in wedged H-type configuration for stability and precision and pole face conductors for focusing and compensation of aberrations. The concept was derived analytically, refined with the OPERA 2D software and tested with the ray-tracing module of OPERA 3D.

Highlights of the ISOLDE facility and the HIE-ISOLDE project

The ISOLDE facility is an ISOL-based radioactive beam facility at CERN. It is dedicated to the production and research of nuclei far from stability. Exotic nuclei of variety of chemical elements are available for the study of nuclear structure, nuclear astrophysics, fundamental symmetries and atomic physics, as well as for applications in condensed-matter and life sciences. Since longer than a decade it has offered the largest variety of post-accelerated radioactive beams in the world. In order to broaden the scientific opportunities beyond the present ISOLDE facility, the on-going HIE-ISOLDE (High Intensity and Energy) project will provide major improvements in energy range, beam intensity and beam quality. The first phase will boost the beam energy of the current REX LINAC to 5.5MeV/u resulting in larger cross sections for Coulomb excitation compared to the previous maximum energy of 3MeV/u. Higher energies will also open up many transfer reaction channels. Physics with post-accelerated beams starts in autumn 2015. The second phase of the project is already approved and is expected to be completed in 2018 allowing beam energies up to 10MeV/u for A/q=4.5. In this contribution the present status of the ISOLDE facility including some highlights will be discussed. The HIE-ISOLDE project will be described together with a panorama of the physics cases to be addressed.

Highlights of the ISOLDE facility and the HIE-ISOLDE Project

The ISOLDE Radioactive Beam Facility is the dedicated CERN installation for the production and acceleration of radioactive nuclei far from stability. Exotic nuclei of most chemical elements are available for the study of nuclear structure, nuclear astrophysics, fundamental symmetries and atomic physics, as well as for applications in condensed-matter and life sciences. Since more than a decade it offers the largest variety of post-accelerated radioactive beams in the world today. In order to broaden the scientific opportunities beyond the reach of the present facility, the on-going HIE-ISOLDE (High Intensity and Energy) project will provide major improvements in energy range, beam intensity and beam quality. Post-accelerated beams will be available already this year boosting the beam energy of the current REX LINAC to 4.3 MeV/u reaching 5.5 MeV/u next spring. In this new energy regime the Coulomb excitation cross sections are strongly increased with respect to the previous energy of bearly 3 MeV/u and many transfer reaction channels will open. The second stage of the energy upgrade will allow energies of the beam up to 10 MeV/u for the worst scenario of A/q = 4.5. The funds are already secured and it is expected to be completed in 2017. In this contribution the present status of the ISOLDE facility will be discussed, some highlights will be briefly described to illustrate the advances of the facility. The HIEISOLDE project will be described together with a panorama of the physics cases to be addressed in the near future with emphasis in the day-one experiment to be done this year.

Highlights of the ISOLDE Facility and the HIE-ISOLDE Project

The ISOLDE Radioactive Beam Facility is the dedicated CERN installation for the production and acceleration of radioactive nuclei far from stability. Exotic nuclei of most chemical elements are available for the study of nuclear structure, nuclear astrophysics, fundamental symmetries and atomic physics, as well as for applications in condensed-matter and life sciences. Since more than a decade it offers the largest variety of post-accelerated radioactive beams in the world today. In order to broaden the scientific opportunities beyond the reach of the present facility, the on-going HIE-ISOLDE (High Intensity and Energy) project will provide major improvements in energy range, beam intensity and beam quality. Post-accelerated beams will be available already this year boosting the beam energy of the current REX LINAC to 4.3 MeV/u reaching 5.5 MeV/u next spring. In this new energy regime the Coulomb excitation cross sections are strongly increased with respect to the previous energy of bearly 3 MeV/u and many transfer reaction channels will open. The second stage of the energy upgrade will allow energies of the beam up to 10 MeV/u for the worst scenario of A/q = 4.5. The funds are already secured and it is expected to be completed in 2017. In this contribution the present status of the ISOLDE facility will be discussed, some highlights will be briefly described to illustrate the advances of the facility. The HIEISOLDE project will be described together with a panorama of the physics cases to be addressed in the near future with emphasis in the day-one experiment to be done this year.

ISOLDE highlights and the HIE-ISOLDE project

The ISOLDE facility has as objective the production, study and research of nuclei far from stability. Exotic nuclei of most chemical elements are available for the study of nuclear structure, nuclear astrophysics, fundamental symmetries and atomic physics, and for applications in condensed-matter and life sciences. The most recent highlights are presented. The on-going upgrade, the HIE-ISOLDE project, is discussed. HIE-ISOLDE aims to improve the ISOLDE capabilities in a wide front, from an energy increase of the post-accelerated beam to improvements in beam quality and beam purity. The first phase of HIE-ISOLDE will start for physics in the autumn of 2015 with an upgrade of energy for all post-accelerated ISOLDE beams up to 5.5 MeV/u. The proposed day-one experiments are summarized.

Radiation protection study related to the future post-accelerator of the HIE-ISOLDE project

The HIE-ISOLDE project aims at expanding the physics programme of the ISOLDE facility at CERN. In particular, the addition of a superconducting linac will allow the post-acceleration of radioactive ion beams up to 10 MeV/u. However, because of field emission in the superconducting cavities and the possibility of neutron production for ion interactions above the Coulomb barrier, new radiological hazards need to be mitigated. Measurements of dose rate levels close to cavity prototypes were used to determine the intensity of the source of X ray due to field emission for a single cavity. The results were extrapolated to the operation of the 32 cavities that will be installed, and a detailed FLUKA calculation was performed to determine the required shielding to minimise the exposure of personnel present in the ISOLDE experimental hall during operation. FLUKA was also used to determine the maximum ambient dose equivalent rate levels in the accessible part of the hall due to ion beam losses for the envelope energies and intensities.

Beam dynamics design studies of a superconducting radioactive ion beam postaccelerator

Instituut voor Kern-en Stralingsfysica, K.U. Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium(Received 6 October 2010; published 17 February 2011)The HIE-ISOLDE project at CERN proposes a superconducting upgrade to increase the energyrange and quality of the radioactive ion beams produced at ISOLDE, which are currently postaccel-erated by the normal conducting radioactive ion beam experiment linac. The specification and designchoices for the HIE-ISOLDE linac are outlined along with a comprehensive beam dynamics studyundertaken to understand and mitigate the sources of beam emittance dilution. The dominant cause oftransverse emittance growth was attributed to the coupling between the transverse and longitudinalmotions through the phase dependence of the rf defocusing force in the accelerating cavities. Aparametric resonance induced by the coupling was observed and its excitation surveyed as a functionof transverse phase advance using numerical simulations and analytic models to understand and avoidthe regions of transverse beam instability. Other sources of emittance growth were studied and wherenecessary ameliorated, including the beam steering force in the quarter-wave resonator and theasymmetry of the rf defocusing forces in the solenoid focusing channel. A racetrack shaped beamport aperture was shown to improve the symmetry of the fields in the high- quarter-wave resonatorand reduce the loss of acceptance under the offset used to compensate the steering force. Themethods used to compensate the beam steering are described and an optimization routine written tominimize the steering effect when all cavities of a given family are offset by the same amount, takinginto account the different velocity profiles across the range of mass-to-charge states accepted. Theassumptions made in the routine were shown to be adequate and the results well correlated with thebeam quality simulated in multiparticle beam dynamics simulations. The specification of the designtolerances is outlined based on studies of the sensitivity of the beam to misalignment and errors, withparticular emphasis on the phase and amplitude stability required for the independently phasedquarter-wave resonators.