Search

In the framework of the SPES Radioactive Beam Facility of INFN, a dedicated Ion Source R&D program has recently been started at the Legnaro Laboratory. The main goal is to study and improve its quality. The measurements of transverse phase space distributions of the ions produced in the target complex are of great importance for every ISOL based facility like for example SPES. In particular the phase space distribution becomes essential for the determination of simulation parameters and hence for the mass separation, the injection into traps and breeders, calculation of transport losses, etc. For these reasons a new beam emittance analyzer device, developed at the Legnaro laboratories, has recently been coupled with an off-line target front-end. The experimental measurements on the SPES surface ion source, using three different stable ion beams (Rb, Cs, Al), and their analysis, are presented here.

SRFQ2 is the second RFQ superconducting (SC) structure of PIAVE, the positive ion injector of the SC LINAC for heavy ions ALPI, in operation at Legnaro. During 2001, SRFQ2 was extensively tested at cryogenic temperature reaching its design performance, i.e., 280 kV inter-electrode voltage (equivalent to 25 MV/m peak surface electrical field) at 7 W dissipated power. This paper describes the treatments, the main difficulties arisen during the tests, the way they were overcome and the measurement sequences that allowed the characterization of SRFQ2 behavior. A brief description of future programs is also given.

The construction of the low β section of ALPI, the superconducting booster at Laboratori Nazionali di Legnaro, has been started. The 80 MHz buncher cryostat was installed and the first, preliminary test during a machine run was performed. The results confirm that the foreseen mode of operation is sufficient to overcome the mechanical instabilities at the field level of 3 MV/m required by ALPI. The rf performance of the low β resonator suggests that this operating field level could be increased significantly (almost doubled). Preliminary results of experiments on a new fast tuner are reported.

The commissioning phase of the ALPI post-accelerator started at the beginning of 1994 with the installation of the medium beta section (β = 0.11). Test beams of different injection energies and ion species have been accelerated with ALPI and delivered to the experimental halls. The main components of the post-accelerator, namely the cryogenic plant, the pulsing system, the optical and diagnostic elements for the beam transport, the vacuum, rf and control systems was widely tested under different conditions. The average accelerating field over the 44 installed superconducting lead on copper resonators turns out to be 2.5 MV/m and the phase locking procedure for the 48 resonators (accelerating and buncher cavities) is normally completed in about 10 hours. The overall beam transmission towards the post-accelerator is 70% with the DC beam and up to 50% with the pulsed and accelerated beam with currents on the target of the order of some p nA.

A new Radioactive Ion Beam (RIB) facility (SPES) is presently under construction at the Legnaro National Laboratories of INFN. The SPES facility is based on the ISOL method using an UCx Direct Target able to sustain a power of 8 kW. The primary proton beam is provided by a high current Cyclotron accelerator with energy of 35-70 MeV and a beam current of 0.2-0.7 mA. Neutron-rich radioactive ions are produced by proton induced fission on an Uranium target at an expected fission rate of the order of 1013 fissions per second. After ionization and selection the exotic isotopes are re-accelerated by the ALPI superconducting LINAC at energies of 10A MeV for masses in the region A=130 amu. The expected secondary beam rates are of the order of 107 - 109 pps. Aim of the SPES facility is to deliver high intensity radioactive ion beams of neutron rich nuclei for nuclear physics research as well as to be an interdisciplinary research centre for radio-isotopes production for medicine and for neutron beams.

The off-line front-end apparatus of the Selective Production of Exotic Species (SPES) project, developed at the Laboratori Nazionali di Legnaro (LNL) in Italy, involves a number of subsystems and procedures that are potentially dangerous for both human operators and equipments. Among the most potentially dangerous systems are: the high voltage power supply, the ion source complex power supplies, the target chamber handling mechanisms and the laser source. In order to prevent possible injuries to the operators and damages to the equipments, a safety interlock system and logic monitoring have been developed, tested and are now in operation. The solution is based on Schneider Electrics Preventa family safety modules with capability to control the power supplied to critical subsystems in conjunction with safety detectors for critical variable monitoring. Moreover, a Programmable Logic Controller (PLC),model BMXP342020 from the Schneider Electrics Modicon M340 family, is used to monitor the status of the syste...

A 5 MHz phase stabilizing system and beam current monitor for the superconducting linac ALPI at Laboratori Nazionali di Legnaro (LNL) was designed, constructed and tested. The system, based on a 5 MHz resonant phase detector, provides stabilization of the phase of the beam bunches produced by the LNL double drift buncher. In addition, the system gives a non-destructive reading of the pulsed beam current in the range between 0.3 and 140 nA. The high impedance coupling of the preamplifier to the resonant phase detector allows for a sensitivity of 1 mV/nA, which is two orders of magnitude higher than previously reported for this kind of devices. The fast phase stabilization is performed by means of a voltage controlled phase shifter; the long term drifts are corrected using a digitally controlled delay. An automatic phase adjustment of the resonator amplifier output was included, in order to correct for any phase shift generated by the amplifiers due to changes of the input signal level. A general expression of the phase response in resonant phase detectors is evaluated and discussed.

This paper describes the method and instruments used to control the field and phase of the ALPI cavities, and, in particular, presents some software tools recently developed to assist the linac operator in tuning and locking the resonators.

The status of the project for the construction of the ALPI superconducting linear accelerator is described, with information on the building, the radiation shield, the beam transport system, the cryogenic system, the machine cryostats, the power and cooling plants, the pulsing system, the beam diagnostic system, the control system, the installation of the resonators in the machine, the niobium QWR development, and the 14.4 GHz electron cyclotron resonance ion source. Details on the plating experience with large scale production of resonators at LNL are also given.

The project of a superconducting linac acting as booster of the LNL-XTU tandem is briefly discussed. Experience with lead plated quarter wave resonators is discussed together with the machine configuration.

The construction of a positive ion injector for the linac ALPI, named PIAVE, at Laboratori Nazionali di Legnaro was funded in 1996. The beam parameters of the injector, consisting of two superconducting radiofrequency quadrupoles (SRFQ) and eight superconducting quarter wave resonators (QWR) for an equivalent voltage of about 8 MV (U/sup 28+/ beam), are fixed. The building is ready, infrastructures and beam transport lines are being ordered. The superconducting RFQs are in the prototyping phase. The general status of the project is reported in this paper, including cryostat and cryogenics, bunching systems, diagnostic devices and electronic control systems.

The SPES (Selective Production of Exotic Species) project for a national exotic beam facility in Legnaro includes pivotal upgrades of the existing superconducting linac ALPI (Acceleratore Lineare Per Ioni), to make it appropriate as the RIB (Radioactive Ion Beam) accelerator. The new injector, consisting of an Electron Cyclotron Resonance (ECR)-type charge breeder and a radiofrequency quadrupole (RFQ), will be described. Upgrade measures in ALPI to improve beam transmission and final energy, and handle low-intensity RIB will be explained, with the aim of increasing transmission to T > 90%, Ef by ~ 20%, reaching 10 MeV/u for the reference beam 132 Sn.

A four-channel analog-to-digital converter (ADC) for data acquisition in nuclear physics experiments has been developed on a VME board. The circuit architecture is a multistretcher configuration based on a fast conversion module. The board can operate either in sampling or in autotrigger mode with an input range of 4.096 or 8.192 V; the risetime protection can vary from 1 to 32 mu s. Many functions are software selectable; the most significant are: the linear gate trigger mode, the risetime protection, and the ability to set of the low and high thresholds independently for each channel. The conversion module is based on a two-step concept: an overall resolution of 12 b, with a conversion time lower than 1 mu s, is obtained by means of two 8-b flash ADCs and a sliding-scale compensation technique is used to improve the differential linearity. The differential linearity error is less than 1%, while the integral linearity error is 0.023% over the 98% of the dynamic range. >

The aim of the SPES (Selective Production of Exotic Species) project is to provide high intensity and high-quality beams of neutron-rich nuclei to perform forefront research in nuclear structure, reaction dynamics and interdisciplinary fields like medical, biological and material sciences. SPES is a second generation ISOL radioactive ion beam facility, part of the INFN Road Map for the Nuclear Physics and supported by the italian national laboratories LNL (Legnaro) and LNS (Catania). It represents an intermediate step toward the future generation European ISOL facility EURISOL. It is based on the ISOL method with an UCx Direct Target able to sustain a power of 10 kW. The primary proton beam will be delivered by a Cyclotron accelerator with an energy of more then 40 MeV and a beam current of 200 μA. Neutron-rich radioactive ions will be produced by Uranium fission at an expected fission rate in the target of the order of 1013 fissions per second. The exotic isotopes will be re-accelerated by the ALPI superconducting LINAC up to energies of 10-13 AMeV, for masses in the region of A=130 amu, with an expected rate on the secondary target of 108 pps.

A multiparameter data acquisition system to test heavy ion detectors is described. Its modular design, based on the VME bus, allows a real time analysis of the collected events using Motorola 68020 microprocessors. A popular personal computer, directly linked to the VME bus, is used as control station and for the graphical representation of the data. Interface to NIM ADC as well as CAMAC interface are available; mass storage as disk or magnetic tape can be added.

The authors consider the MANDA (Multiprocessor Applied to Nuclear Data Acquisition) systems. They describe the running version of the system, which has been coupled to a double front-end. The data-sorting in this case is accomplished by hardware using CAMAC histogramming memories. Software data analysis is available on the Vaxstation. Some development details concerning the coupling with new front ends and the VME online data analysis system are given. >

The impetuous progress of the detection systems in nuclear medicine are based on major improvements of the sensitivity of the new detector systems and on the highly-integrated low-noise associated electronics, offering valuable solutions for the diagnostic of premature biological lesions. Most of the presently available detectors for nuclear medicine employ mechanical collimation, which couples the detection sensitivity to the spatial resolution. The electronic collimation of Compton cameras can overcome this drawback, but drastically reduces the efficiency due to the coincidence measurement. However, the Compton imaging systems can offer advantages over the traditional ones and the study of innovative solutions involving the newest available detectors and electronics could lead to unexpectedly good results. Our goal is to design a Compton camera based on Si-pad detectors and ASIC electronics. We performed extensive Monte Carlo simulations for systems consisting of Si-pad detectors with various thickness and pad dimensions, as well as for different geometries. The various Si-pad detectors were characterized before the bonding to the ASIC electronics and the whole assembly was subsequently tested with a VA-DAQ acquisition system from IDEAS. The results of the characterization measurements and tests will be presented

MANDA-LAB is a multiprocessor system based on VMEbus mainly intended for detector (and front-end electronics) tests used in heavy ion physics. A popular personal computer, as control station, is directly linked to the VMEbus, where commercially available cards allow ''real time analysis'' of the collected events. A widely used software package for analysis has been migrated to the multiprocessor environment of the system. Flexibility and ''user friendly'' interface are the main goal of the system. The availability of interface to CAMAC and Ethernet, and the modularity of hardware and software allow a free expansion of the system.