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Modern particle accelerator projects, such as MYRRHA, have very high stability and/or reliability requirements. To meet those, it is necessary to optimize or develop new methods for the control systems. One of the difficulties lies in the relatively long computation time of current beam dynamics codes. In this context, the very low computation time of neural network is of great attraction. However, a neural network has to be trained in order to be of any use. The training of a beam dynamic predictor uses a large dataset (experimental or simulated) that represents the dynamics over the parameter space of interest. Therefore, choosing the right training dataset is crucial for the quality of the neural network predictions. In this work, a study on the sampling choice for the training data is performed to train a neural network to predict the transmission of a beam through a low energy beam transport line and a Radiofrequency Quadrupole. We show and discuss the results obtained on training data set to model the IPHI and MYRRHA injectors., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

Presented at the XXXIV Mazurian Lakes Conference on Physics, Piaski, Poland, September 6–13, 2015, During the last years, the ECOS working group has been considering the construction of a new high-intensity accelerator of stable ion beams for the next Long-Range Plan of the nuclear physics community in Europe. The new facility (LINCE) will be a multi-user facility dedicated to ECOS science: fundamental physics, astrophysics, nuclear structure and reaction dynamics. In this paper, we summarize preliminary design studies of the low-energy part of this facility based on the use of a multi-ion supercon- ducting linac., Work partially supported by the Spanish Government under the grant Feder-Interconnecta “Aceltec” ITC-20111070. The authors are also grateful to the companies Alter Technology-Tüv, Avs, Cibernos, Elitt Energy, Faysol, Idom, and Tti Norte for partial funding of this work and active participation in the design and prototyping carried-out in this study.

A single crystal diamond detector (SC-DD) has been used to obtain the time structure of bunches with lengths between 4 and 88 ns. This was achieved by setting an electronic chain based on a time-to-amplitude converter (TAC), which used the output of the diamond detector as the start of the time interval, and the accelerator RF as the stop. Moreover, the SC-DD not only provided the time information, but also the energy of the beam.

In order to probe neutron rich radioactive noble gases produced by photo-fission, a PARRNe-1 experiment (Production d’Atomes Radioactifs Riches en Neutrons) has been carried out at CERN. The incident electron beam of 50 MeV was delivered by the LIL machine: LEP Injector Linac. The experiment allowed us to compare under the same conditions two production methods of radioactive noble gases: fission induced by fast neutrons and photo-fission. The obtained results show that the use of the electrons is a promising mode to get intense neutron rich ion beams. After the success of this photo-fission experiment, a conceptual design for the installation at IPN Orsay of a 50 MeV electron accelerator close to the PARRNe-2 device has been worked out: ALTO Project. This work has started within a collaboration between IPNO, LAL (Laboratoire de l’Accelerateur Lineaire) and CERN groups.

The copper coating has been proposed to stiffen the niobium superconducting cavity in order to reduce its deformations under Lorentz forces. The environment of thermal spray process is very important to get the wanted copper properties, as a consequence, the Inert Plasma Spray (IPS) process was used to realize the copper coating onto niobium. With the use,of X-ray diffraction method, the radiocrystallographic elastic constants (REC) of the IPS copper coating have been measured firstly, and then, in using the measured REC, the residual stress distribution has been determined secondly as a function of the depth in the copper coating and in the substrate.

Uppsala University is constructing a large scale facility, called FREIA (Facility for Research Instrumentation and Accelerator Development). FREIA includes a helium liquefier and an accelerator test facility and has the capacity to test superconducting radio-frequency (RF) cavities with the same RF system and RF power level as in an accelerator. A central element of FREIA is a horizontal test cryostat connected in closed loop to a helium liquefier. This cryostat can house two fully equipped (tuners, piezo, power coupler, helium tank) superconducting cavities to perform full RF high power tests and operate at temperatures between 1.8 K and 4.2 K. The cryostat is designed to accommodate a large array of superconducting cavities and magnets, among which the European Spallation Source (ESS) type spoke and high-β elliptical cavities as well as TESLA/ILC type elliptical cavities. The present status of the project and the design of the cryostat are reported.

Heat transfer from a plane surface to a saturated He II bath is studied up to and beyond the critical heat flux density q ∗ inducing film boiling. The experiments were performed with two similar test cells, denoted 1 and 2. Test cell 2 consists mainly of four OFHC copper rods heated at their top extremity and equipped each with three calibrated carbon resistors for in situ measurement of the thermal conductivity k Cu (T). Three of these test specimens are equipped with specially developed surface thermometers. The measured Kapitza conductance at high heat flux ( q ≤ 5 × 10 4 W m −2 ) as well as k Cu versus T data (temperature range 2–6 K) presents a good reproducibility between the four samples tested. The heat transfer characteristics were recorded at T bath = 1.8 K for different immersion depths H 0 of the heat transfer surface and the results are discussed. We also report on the experimental q ∗ versus H 0 data. These data measured on both test specimens either equipped or not equipped with surface thermometers, show a strong dependence of q ∗ on the sample surface cooling conditions.

Accelerating gradients Eacc=26 MV/m with a world record Q of 3/spl times/10/sup 10/ in 9-cell TESLA superconducting RF (SRF) cavities have been reached in CW and pulsed RF modes. On the way to reaching the excellent performance, we experimentally characterized quench natures (most serious obstacle to higher gradients), investigated the Kapitza conduction and boiling heat transfer between cavities and LHe II, and studied the quench behaviors both in He II and normal LHe. Finally, we discuss the possibilities of further greatly raising the accelerating gradients to 50-100 MV/m by use of Nb/sub 3/Sn and some HTc superconducting materials.

Accelerator Driven Systems (ADS) for nuclear waste transmutation require proton drivers with energies between 600 and 800 MeV and beam currents of several mA for demonstrators and up to 25 mA for large industrial systems. Within the EUROTRANS project a 600 MeV linac has been designed to meet the stringent requirements regarding reliability, availability and extreme low beam losses. The first accelerating section using the novel CH‐cavity accelerates the beam to 17 MeV at the injection point into the main linac. The intermediate energy section (17–100 MeV) of the main linac consists of superconducting independently phased spoke‐type cavities followed by the high energy section consisting of 704 MHz superconducting elliptical cavities. The paper covers the development of the linac, prototype testing and reliability considerations of the whole EUROTRANS project.

This document identifies and discusses the proper design strategies that have been followed in order to meet the reliability and availability specifications for a high intensity proton accelerator meant as the spallation neutron driver for an eXperimental Driven System (XADS) for nuclear waste transmutation. The document describes also how these strategies can be applied in the different components of the XADS accelerator design, and how design iterations can lead to reliability improvements. The Failure Mode and Effect Analysis (FMEA) methodology has been used on the suggested design for highlighting the reliability critical areas. Finally, a first rough cost estimation of the XADS accelerator is also provided.

Stiffening of bulk niobium SRF cavities is mandatory for reducing the frequency shift induced by Lorentz forces at high accelerating gradients. Experimental and computational data previously reported show that with the actual scheme (i.e. EB welded stiffening rings) the frequency shift of TESLA 9 cells SRF cavities is higher than the cavity bandwidth above Eacc=28 MV/m. We propose a new stiffening method, using a Plasma Sprayed Copper Layer (PSCL) onto bulk niobium cavities. As compared to the actual technique, this method offers several advantages (simplicity, reliability...). The first experimental data obtained with monocell cavities produced by this method demonstrate the efficiency of cavities stiffening with plasma spraying. Thermal and mechanical properties measured on niobium samples with a PSCL are also presented. These data will allow us choose the plasma spraying process suitable for achieving the best cavities performances.

The thermal behaviour of a "fish hook" type HOM coupler for superconducting RF Cavities is analyzed by numerical simulation using a 3D finite element based code for both CW (rings, recirculating linacs) and pulsed (s.c. colliders studies like TESLA) accelerator types. Consequently, a thorough study of the thermal stability of this system is necessary in both transient and steady-state regimes. Numerical simulations, assuming anomalous losses at the end of the HOM inner conductor, were performed. The effects of the HOM coupler geometry and the materials thermal conductivity on the critical heat flux inducing the quench of the system are discussed. >

MACSE, a pilot accelerator, has been built at Saclay in order to fully develop the technology of superconducting electron linacs. It consists of five niobium cavities powered by five klystrons. The 1.5-GHz, 5-cell cavities are equipped with coaxial couplers. The first cavity has a reduced phase velocity to capture the 100-kV electrons coming from the injector. It is followed by a four-cavity cryomodule. The present status and the first beam test are reported, along with some results of superconductivity R&D. >

The performance of high gradient superconducting RF cavities for electron accelerators is mainly limited by field emission. Major improvements have been recently obtained using different surface conditioning techniques confirming the involvement of metallic particles in field emission enhancement. In this paper we present the results obtained with an optical apparatus attached to an RF copper cavity equipped with a removable sample which is subjected to high RF fields (E/sub pk/>40 MV/m). Stable light spots are observed on the sample surface and their intensities and optical spectra are measured as a function of the surface electric field. The total emitted current is simultaneously measured by an isolated hollow electrode facing the sample. Particles of different types were deliberately sprinkled over the sample surface and the luminous features are studied. Light intensity, spectral power density and evolution of the luminous sites provide useful information for understanding the field emission phenomena and the conditioning effects.

An advanced rotating temperature and radiation mapping has been developed for investigation of field emission and thermal breakdown of TESLA 9-cell superconducting cavities in superfluid He. More than 10,000 spots on cavity surfaces can be investigated in one turn with 5/spl deg/ angular stepping. We locate a heated area with maximum /spl Delta/T=3.3 K around the 5th cell's equator. A heat flux density of 5 W/cm/sup 2/ in the region /spl Delta/T=3 K and total heat power Q/spl sim/100 W going to LHe from the area were calculated. An emitter responsible for the heating was identified at the iris area (So=8 cm) of the same cell according to T-maps associated with a simulation of impacting electron trajectories. The cavity reached Eacc=20 MV/m. We briefly introduce the technical layout, experimental data and analysis results.

International audience; A 500 MeV, 1.3 GHz superconducting linear accelerator is being studied and built to serve as a test facility for the TESLA linear collider project. The phase 1 injector, having an energy of 8-14 MeV and an intensity of 8 mA with a high duty cycle (800 microseconds, 10 Hz repetition rate), consists of a 250 keV electron gun, a 216.7 MHz subharmonic buncher and a superconducting capture cavity at the main linac frequency. The main characteristics (intensity, position, emittance, bunch length, energy spread) are to be measured using different techniques. A particular effort will be made on the use of optical transition radiation (OTR) for the determination of the transverse beam emittance as well as the bunch length. The injector, involving, the participation of three French laboratories (LAL, CEA/DAPNIA, IPN), will be tested partly in France (Orsay-Saclay) and then completely at DESY (Hamburg)

In this work, the influence of the thermal spraying processes, atmospheric plasma spraying (APS), high velocity oxygen fuel (HVOF), and vacuum plasma spraying (VPS), on the microstructure and properties of copper coatings is discussed. The differences in microstructure, microhardness, and residual stress for each type of coating are shown. The X-ray diffraction (XRD) method is used to evaluate the mechanical anisotropical characteristics of the materials and the residual stress distribution. The particularity of this study is that the thickness of the coating is of the millimetre scale; the massive coating specimens without a substrate were obtained for XRD microelastic modulus measurements and for macrotensile measurement. Microhardness distributions have been obtained in coatings and in substrates that pass through the interface zones. It was observed that dense coatings could be obtained by industrial processes such as APS and HVOF, but they induce oxidation in the copper coating. The copper ox...

17th IEEE Particle Accelerator Conference, PAC 97, Vancouver, USA, 12 May 1997 - 16 May 1997; 65 pp. (1997)., Following tests of the various sub-assemblies at Saclay and Orsay, installation of the entire TESLA Test Facility Injector was completed in Hall 3 at DESY in December 1996. The first phase of operation employs a 250 kV thermionic electron source providing an 800 ms train of bunches, each containing 37 pC, and followed by a 216.7 MHz pre-bunching cavity. Subsequent bunching and acceleration is achieved using a standard 1.3 GHz superconducting 9 cell TESLA cavity operated in pulsed mode (10 Hz). Prior to injection in the main linac, the beam parameters are verified using a spectrometer consisting of a dipole magnet and SEM profile monitor. Once the beam is adjusted it is transported to the linac using an optical matching system employing two triplets. We present results of the first beam tests of the completed injector which took place early in 1997.

We describe the peripherical elements of CRYEBIS such as the electronics and the high voltage terminal. The results of the three main experimental series are given and discussed. Ions such as Ne 10+ , A 18+ , Kr 34+ and Xe 44+ are available with such a device which needs a long time for adjustment before being used on a machine.

An accelerator for 75(Q/A)2 MeV/amu heavy ion beams with ability to produce by stripping a rather large Q/A ratio — at least 0.285 in the 40 – 80 mass range — is now in operation in Orsay. As previously described, ALICE consists of a Linac (Q/A ≥ 0.08) acting as an injector at 1.15 MeV/amu and a sector‐focused isochronous cyclotron.505 MeV Kr24+, 475 MeV Kr23+ (10−10 − 2·10−10 A particle current) and 227 MeV Ar11+, 300 MeV Ar13+ (4·10−9 – 8·10−9 A particle current) are the most used beams since 1971, with an operation time of about 70%Different improvements of the conceptual design have been needed to obtain these results, the principal one being on the platform where the PIG ion source has been put in an analysing magnet (5 kG) with an improved vacuum (10−6 Torr). The efficiency of the main components is discussed, and some future improvements are proposed. With a view to satisfying an increasing demand, a new beam transport system has been designed (9 lines) and its installation is planned for December,...