Probabilistic Routing for On-Street Parking Search

An estimated 30% of urban traffic is caused by search for parking spots [Shoup, 2005]. Suggesting routes along highly probable parking spots could reduce traffic. In this paper, we formalize parking search as a probabilistic problem on a road graph and show that it is NP-complete. We explore heuristics that optimize for the driving duration and the walking distance to the destination. Routes are constrained to reach a certain probability threshold of finding a spot. Empirically estimated probabilities of successful parking attempts are provided by TomTom on a per-street basis. We release these probabilities as a dataset of about 80,000 roads covering the Berlin area. This allows to evaluate parking search algorithms on a real road network with realistic probabilities for the first time. However, for many other areas, parking probabilities are not openly available. Because they are effortful to collect, we propose an algorithm that relies on conventional road attributes only. Our experiments show that this algorithm comes close to the baseline by a factor of 1.3 in our cost measure. This leads to the conclusion that conventional road attributes may be sufficient to compute reasonably good parking search routes

Beam Based Alignment of Focusing Solenoids at ARES

ARES is an electron linear accelerator at the SINBAD facility at DESY. It aims to deliver reliable high-brightnessbeams with an energy in the range of 50 MeV to 150 MeVwith fs to sub-fs bunch lengths. This is ideal for injection intonovel high-gradient acceleration devices, such as dielectriclaser accelerators (DLA), accelerator components R&D andmedical applications. The ARES linac has been recentlycommissioned. Here we report the results of beam basedalignment of focusing solenoids of ARES. The alignmentis an important part of commissioning and is crucial for thebeam quality

Quasiparticle tunneling in the lowest Landau level

ISSN:1098-0121ISSN:0163-1829ISSN:1550-235XISSN:0556-2805ISSN:2469-9969ISSN:1095-379

Characterization of relativistic electron bunch duration and travelling wave structure phase velocity based on momentum spectra measurements on the ARES linac at DESY

The ARES linac at DESY aims to generate and characterize ultrashort electron bunches (fs to sub-fs duration) with high momentum and arrival time stability for the purpose of applications related to accelerator R&D, e.g. development of advanced and compact diagnostics and accelerating structures, test of new accelerator components, medical applications studies, machine learning, etc. During its commissioning phase, the bunch duration characterization of the electron bunches generated at ARES has been performed with an RF-phasing technique relying on momentum spectra measurements, using only common accelerator elements (RF accelerating structures and magnetic spectrometers). The sensitivity of the method allowed highlighting different response times for Mo and Cs2Te cathodes. The measured electron bunch duration in a wide range of machine parameters shows excellent agreement overall with the simulation predictions, thus demonstrating a very good understanding of the ARES operation on the bunch duration aspect. The importance of a precise in-situ experimental determination of the phase velocity of the first travelling wave accelerating structure after the electron source, for which we propose a simple new beam-based method precise down to sub-permille variation respective to the speed of light in vacuum, is emphasized for this purpose. A minimum bunch duration of 20 fs rms, resolution-limited by the space charge forces, is reported. This is, to the best of our knowledge, around 4 times shorter than what has been previously experimentally demonstrated based on RF-phasing techniques with a single RF structure. The present study constitutes a strong basis for future time characterization down to the sub-fs level at ARES, using dedicated X-band transverse deflecting structures

Photocathode Charge Map Measurements at ARES

The ARES linac at DESY (Deutsches Elektronen-Synchrotron) is a dedicated accelerator research and development facility for advanced accelerator technologies and applications, including high gradient accelerating schemes, high-resolution diagnostics and medical applications. It provides ultra-short, high quality electron beams with charges between a few femtocoulombs and a few hundred picocoulombs, with energies up to 155 MeV, characterized by high reproducibility and stability. The electron bunches are generated in a photoinjector comprising a UV laser and a normal conducting S-band gun with an exchangeable cathode material, enabling the required wide charge range and temporal bunch profile. A set of movable mirrors allows to change the position of the laser spot on the cathode, which in combination with bunch charge diagnostics downstream of the gun can be used for measuring the extracted charge as a function of the laser position. With this method the emission homogeneity and changes of the cathode can be studied and different cathode materials can be compared. We present the first results using this technique at ARES, including charge map and quantum efficiency (QE) measurements

Commissioning Results and Electron Beam Characterization with the S-Band Photoinjector at SINBAD-ARES

Over the years, the generation and acceleration of ultra-short, high quality electron beams has attracted more and more interest in accelerator science. Electron bunches with these properties are necessary to operate and test novel diagnostics and advanced high-gradient accelerating schemes, such as plasma accelerators and dielectric laser accelerators. Furthermore, several medical and industrial applications require high-brightness electron beams. The dedicated R&D facility ARES at DESY (Deutsches Elektronen-Synchrotron) will provide such probe beams in the upcoming years. After the setup of the normal-conducting, radio-frequency (RF) photoinjector and linear accelerating structures, ARES successfully started the beam commissioning of the RF gun. This paper gives an overview of the ARES photoinjector setup and summarizes the results of the gun commissioning process. The quality of the first electron beams is characterized in terms of charge, momentum, momentum spread and beam size. Additionally, the dependencies of the beam parameters on RF settings are described. All measurement results of the characterized beams fulfill the requirements for operating the ARES linac with this RF photoinjector

Commissioning Results and Electron Beam Characterization with the S-Band Photoinjector at SINBAD-ARES

Over the years, the generation and acceleration of ultra-short, high quality electron beams has attracted more and more interest in accelerator science. Electron bunches with these properties are necessary to operate and test novel diagnostics and advanced high-gradient accelerating schemes, such as plasma accelerators and dielectric laser accelerators. Furthermore, several medical and industrial applications require high-brightness electron beams. The dedicated R&D facility ARES at DESY (Deutsches Elektronen-Synchrotron) will provide such probe beams in the upcoming years. After the setup of the normal-conducting, radio-frequency (RF) photoinjector and linear accelerating structures, ARES successfully started the beam commissioning of the RF gun. This paper gives an overview of the ARES photoinjector setup and summarizes the results of the gun commissioning process. The quality of the first electron beams is characterized in terms of charge, momentum, momentum spread and beam size. Additionally, the dependencies of the beam parameters on RF settings are described. All measurement results of the characterized beams fulfill the requirements for operating the ARES linac with this RF photoinjector