9. Machine parameters measurements and others
Paper Title Page
MOOA02 Noise in Radio/Optical Communications 1
  • M. Vidmar
    University of Ljubljana, Faculty of Electrical Engineering, Ljubljana, Slovenia
  Noise is a random signal that affects the performance of all electronic and/or optical devices. Although the sources of different kinds of noise have their backgrounds in physics, engineers dealing with noise use different methods and units to specify noise. The intention of this tutorial is to describe the main effects of noise in electronics up to optical frequencies while providing links between the physics and engineering worlds. In particular, noise is considered harmful while degrading the signal-to-noise ratio or broadening the spectrum of signal sources. On the other hand, noise can be itself a useful signal. Finally, artificially generated signals that exhibit many properties of random natural noise are sometimes required.  
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-MOOA02  
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MOPA12 The Design and Use of Faraday Cage in Linac Temporary Line of CSNS 48
  • M. Meng
    DNSC, Dongguan, People's Republic of China
  • F. Li, P. Li, A.X. Wang, T.G. Xu
    IHEP, Beijing, People's Republic of China
  • J.L. Sun
    CSNS, Guangdong Province, People's Republic of China
  In the end of linac temporary line in csns, we need a faraday cage to absorb the beam. in the beam experiment it will be mounted and used twice. according to the beam energy and current of csns, we choose water-cooled pipe structure with tilted panel after simulation. the main principle of the faraday cage design is to simplify the structure and reduce the radiation activation of it, to do this, we also do the simulation of radiation. to make sure the faraday cage is safe in beam experiment, we alos plug in a pt100 Platinum resistance to monitor the temperature. after faraday cage is built and mounted on the line, it works well and sustain the beam bombardment.  
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-MOPA12  
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MOPA13 Fast Luminosity Monitoring for the SuperKEKB Collider (LumiBelle2 Project) 51
  • C.G. Pang, P. Bambade, S. Di Carlo, D. Jehanno, V. Kubytskyi, Y. Peinaud, C. Rimbault
    LAL, Orsay, France
  • Y. Funakoshi, S. Uehara
    KEK, Ibaraki, Japan
  LumiBelle2 is a fast luminosity monitoring system prepared for SuperKEKB. It uses sCVD diamond detectors placed in both the electron and positron rings to measure the Bhabha scattering process at vanishing scattering angle. Two types of online luminosity signals are provided, a Train-Integrated-Luminosity at 1 kHz as input to the dithering feedback system used to maintain optimum overlap between the colliding beams in horizontal plane, and Bunch-Integrated-Luminosities at about 1 Hz to check for variations along the bunch trains. Individual beam sizes and offsets can also be determined from collision scanning. This paper will describe the design of LumiBelle2 and report on its performance during the Phase-2 commissioning of SuperKEKB.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-MOPA13  
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MOPA14 Electron Spectrometer for a Low Charge Intermediate Energy LWFA Electron Beam Measurement 57
  • A.V. Ottmar, Yu.I. Maltseva, T.V. Rybitskaya
    BINP SB RAS, Novosibirsk, Russia
  • V. Gubin
    Institute of Laser Physics, SB RAS, Novosibirsk, Russia
  The Laser-driven Compton light source is under development in ILP SB RAS in collaboration with BINP SB RAS. Electron spectrometer for measurement of LWFA electron beam with energy in the range 10-150 MeV and bunch charge 1-10 pC is presented. Spectrometer based on permanent magnet and luminous screen with CCD registrar and this geometry was optimized for best measurements resolution in compromise with size limitations. Preliminary collimation of electron beam allows achieving energy resolution up to 5-10 % of top limit. System has been tested at the VEPP-5 linear electron accelerator and obtained results correspond to design objectives. Sensitivity of beam transverse charge density was experimentally fixed at 0.03 pC/mm2, it is practically sufficient for our LWFA experiments.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-MOPA14  
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MOPA16 Design of a Compact Permanent Magnet Spectrometer for CILEX/APOLLON 61
  • M. Khojoyan, A. Cauchois, J. Prudent, A. Specka
    LLR, Palaiseau, France
  Laser wakefield acceleration experiments make extensive use of small permanent magnets or magnet assemblies for analyzing and focusing electron beams produced in plasma accelerators. This choice is motivated by the ease of operation inside vacuum chambers, absence of power-supplies and feedthroughs, and potentially lower cost. Indeed, in these experiments space is at premium, and compactness is frequently required. At the same time, these magnets have to have a large angular acceptance for the divergent laser and electron beams which imposes constraint of the gap size. We will present the optimized design and characterization of a 100 mm long, 2.1 Tesla permanent magnet dipole. Furthermore, we will present the implementation of this magnet in a spectrometer that will measure the energy spectrum of electrons of [60-2000] MeV with a few percent resolution in the CILEX/APOLLON 10PW laser facility in France.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-MOPA16  
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MOPA17 Momentum Compaction Measurement Using Synchrotron Radiation 66
  • L. Torino, N. Carmignani, A. Franchi
    ESRF, Grenoble, France
  The momentum compaction factor of a storage ring can be obtained by measuring how the beam energy changes with the RF frequency. Direct measurement of the beam energy can be difficult, long or even not possible with acceptable accuracy and precision in some machines such as ESRF. Since the energy spectrum of the Synchrotron Radiation (SR) depends on the beam energy, it is indeed possible to relate the variation of the beam energy with a variation of the produced SR flux. In this proceeding, we will present how we obtain a measurement of the momentum compaction using this dependence.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-MOPA17  
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MOPB02 ARIES-ADA: An R&D Network for Advanced Diagnostics at Accelerators 71
  • P. Forck, M. Sapinski
    GSI, Darmstadt, Germany
  • C. Gerth, K. Wittenburg
    DESY, Hamburg, Germany
  • U. Iriso, F. Pérez
    ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
  • R. Ischebeck
    PSI, Villigen PSI, Switzerland
  • O.R. Jones
    CERN, Geneva, Switzerland
  Funding: This project has received funding from the European Union's Horizon 2020 Research and Innovation programme under Grant Agreement No 730871.
Accelerator Research and Innovation for European Science and Society, ARIES, is an initiative funded by the European Union (https://aries.web.cern.ch/). The activity comprises three major categories: Joint Research Activities; Transnational Access; Network Activities. One of these networks is related to Advanced Diagnostics at Accelerators (ADA) with the task of strengthening collaborations between international laboratories for coordinated research and development in beam diagnostics (https://aries.web.cern.ch/content/wp8). This task is performed by organizing topical workshops on actual developments and supporting interchange of experts between different labs. Since the start of the project in May 2017 four topical workshops of two to three days duration have been organized, each with 30-40 participants ranging from novices to worldwide experts in their particular field. In this contribution these initial workshops are summarized and an outlook given for further workshops within this ARIES-ADA network.
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MOPB03 High-Energy Scraper System for the S-DALINAC Extraction Beam Line - Commissioning Run* 75
  • L.E. Jürgensen, M. Arnold, T. Bahlo, C. Burandt, R. Grewe, J. Pforr, N. Pietralla, A. Rost, S. Weih, J. Wissmann
    TU Darmstadt, Darmstadt, Germany
  • F. Hug
    IKP, Mainz, Germany
  • T. Kürzeder
    HIM, Mainz, Germany
  Funding: *Funded by Deutsche Forschungsgemeinschaft under grant No. GRK 2128
The S-DALINAC is a thrice recirculating, superconducting linear electron accelerator at TU Darmstadt. It delivers electron beams in cw-mode with energies up to 130 MeV. The high-energy scraper system has been installed in its extraction beam line to reduce the energy spread and improve the energy stability of the beam for the experiments operated downstream. It comprises three scraper slits within a dispersion-conserving chicane consisting of four dipole magnets and eight quadrupole magnets. The primary scraper, located in a dispersive section, allows to improve and stabilize the energy spread. In addition energy fluctuations can be detected. Scraping of x- and y-halo is implemented in two positions enclosing the position of the primary scraper. We will present technical details and results of the first commissioning run of the recently installed system at the S DALINAC. Besides improving on the energy spread, it proved to be a valuable device to observe energy spread and energy fluctuations as well as to reduce background count rates next to the experimental areas.
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MOPB04 Progress in the Stripline Kicker for ELBE 78
  • Ch. Schneider, A. Arnold, J. Hauser, P. Michel
    HZDR, Dresden, Germany
  The linac based cw electron accelerator ELBE operates different secondary beamlines one at a time. For the future different end stations should be served simultaneously, hence specific bunch patterns have to be kicked into different beam-lines. The variability of the bunch pattern and the frequency resp. switching time are one of the main arguments for a stripline-kicker. A design with two tapered active electrodes and two ground fenders was optimized in time and frequency domain with the software package CST. From that a design has been transferred into a construction and was manufactured. The presentation summarises the recent results and the status of the project.  
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MOPB06 DAΦNE Luminosity Monitor 81
  • A. De Santis, C. Bisegni, O.R. Blanco-García, O. Coiro, A. Michelotti, C. Milardi, A. Stecchi
    INFN/LNF, Frascati (Roma), Italy
  The DAΦNE collider instantaneous luminosity has been measured identifying Bhabha scattering events at low polar angle (∼10°) around the beam axis by using two small crystal calorimeters shared with the KLOE-2 experiment. Independent DAQ setup based on !CHAOS, a novel Control System architecture, has been designed and realized in order to implement a fast luminosity monitor, also in view of the DAΦNE future physics runs. The realized setup allows for measurement of Bunch-by-Bunch (BBB) luminosity that allows to investigate the beam-beam interaction for the Crab-Waist collisions at DAΦNE and luminosity dependence on the bunch train structure.  
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MOPB07 Beam Parameter Measurements for the J-PARC High-Intensity Neutrino Extraction Beamline 85
  • M.L. Friend
    KEK, Ibaraki, Japan
  Proton beam monitoring is absolutely essential for the J-PARC neutrino extraction beamline, where neutrinos are produced by the collision of 30 GeV protons from the J-PARC MR accelerator with a long carbon target. Continuous beam monitoring is crucial for the stable and safe operation of the extraction line high intensity proton beam, since even a single misfired beam spill can cause serious damage to beamline equipment at 2.5x1014 and higher protons-per-pulse. A precise understanding of the proton beam intensity and profile on the neutrino production target is also necessary for predicting the neutrino beam flux with high precision. Details of the suite of monitors used to continuously and precisely monitor the J-PARC neutrino extraction line proton beam will be shown, including recent running experiences, challenges, and future upgrade plans.  
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MOPB08 Evaluation of the Transverse Impedanse of Pf in-Vacuum Undulator Using Local Orbit Bump Method 89
  • O. Tanaka, M. Adachi, K. Harada, R. Kato, N. Nakamura, T. Obina, R. Takai, Y. Tanimoto, K. Tsuchiya, N. Yamamoto
    KEK, Ibaraki, Japan
  When a beam passes through insertion devices (IDs) with narrow gap or beam ducts with small aperture, it receives a transverse kick from the impedances of those devices. This transverse kick depends on the beam trans-verse position and beam parameters such as the bunch length and the total bunch charge. In the orbit bump method, the transverse kick factor of an ID is estimated through the closed orbit distortion (COD) measurement at many BPMs for various beam currents [1]. In the present study, we created an orbit bump of 1 mm using four steering magnets, and then measured the COD for two cases: when the gap is opened (the gap size is 42 mm) and when the gap is closed (the gap size is 3.83 mm). The ID's kick factors obtain by these measurements are compared with those obtain by simulations and analytical evaluations.  
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MOPB09 Comparison Among Different Tune Measurement Schemes at HLS-II Storage Ring 93
  • L.T. Huang, X.Y. Liu, P. Lu, M.-X. Qian, B.G. Sun, J.G. Wang, J.H. Wei, F.F. Wu, Y.L. Yang, T.Y. Zhou
    USTC/NSRL, Hefei, Anhui, People's Republic of China
  Tune measurement is one of the most significant beam diagnostics at HLS-II storage ring. When measuring tune, higher tune spectral component and lower other compo-nents are expected, so that the tune measurement will be more accurate. To this end, a set of BBQ (Base Band Tune) front-end based on 3D (Direct Diode Detection) technique has previously developed to improve the effec-tive signal content and suppress other components. Em-ploying the BBQ front-end, four different tune measure-ment schemes are designed and related experiments per-formed on the HLS-II storage ring. Experimental results and analysis will be presented later.  
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MOPB10 A Study on the Influence of Bunch Longitudinal Distribution on the Cavity Bunch Length Measurement 97
  • Q. Wang, Q. Luo, B.G. Sun, F.F. Wu
    USTC/NSRL, Hefei, Anhui, People's Republic of China
  Funding: Supported by National Key R&D Program of China (2016YFA0401900, 2016YFA0401903), NSFC (11375178, 11575181) and the Fundamental Research Funds for the Central Universities (WK2310000046)
Cavity bunch length measurement is used to obtain the bunch length depending on the eigenmodes exciting in-side the cavity. For today's FELs, the longitudinal distribution of particles in electron bunch (bunch shape) may be non-Gaussian, sometimes very novel. In this paper, the influence of bunch shape on the cavity bunch length measurement is analyzed, and some examples are given to verify the theoretical results. The analysis shows that the longitudinal distribution of particles in electron bunch has little influence on the cavity bunch length measure-ment when the bunch length is less than 1 ps and the eigenmodes used in measurement are below 10GHz.
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MOPB13 Active Magnetic Field Compensation System for SRF Cavities 101
  • L.H. Ding
    Laboratory GREYC, Caen, France
  • J. Liang, H. Liu, Z.P. Xie
    Hohai University, Nanjing, People's Republic of China
  • Z.P. Xie
    IMP/CAS, Lanzhou, People's Republic of China
  Abstract: Superconducting Radio Frequency (SRF) cavities are becoming popular in modern particle accelerators. When the SRF cavity is transitioning from the non-conducting to the Superconducting state at the critical temperature (Tc), the ambient magnetic field can be trapped. This trapped flux may lead to an increase in the surface resistance of the cavity wall, which can reduce the Q-factor and efficiency of the cavity. In order to increase the Q-factor, it is important to lower the surface resistance by reducing the amount of magnetic flux trapped in the cavity wall to sub 10mG range during the Tc transition. In this paper, we present a 3-axis automatic active magnetic field compensation system that is capable of reducing the earth magnetic field and any local disturbance field. Design techniques are described to enhance the system stability while utilizing the flexibility of embedded electronics. This paper describes the system implementation and concludes with initial results of tests. Experimental results demonstrate that the proposed magnetic field compensation system can reduce the earth magnetic field to around 2.5 mG even without shielding.  
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MOPB14 SSRF Beam Operation Stability Evaluation Using Bunch by Bunch Beam Position Method* 104
  • N. Zhang
    SSRF, Shanghai, People's Republic of China
  • Y.B. Leng, Y.M. Zhou
    SINAP, Shanghai, People's Republic of China
  Funding: * Work supported by National Natural Science Foundation of China (No.11575282 No.11375255 No.11305253)
In order to improve the efficiency and quality of light in top-up mode at SSRF, disturbance caused by leakage fields mismatch during injection should be minimized and stable. This could be evaluated by analysis of bunch by bunch residual betatron oscillation data, using this method, instability of tune distribution and damping repeatability could also be calculated. So we could evaluate the beam operation stability by the data analysis and discuss in the paper.
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MOPB16 Continuous Beam Energy Measurements at Diamond Light Source 107
  • N. Vitoratou, P. Karataev
    Royal Holloway, University of London, Surrey, United Kingdom
  • P. Karataev
    JAI, Egham, Surrey, United Kingdom
  • G. Rehm
    DLS, Oxfordshire, United Kingdom
  Resonant Spin Depolarization (RSD) is a well-known technique that has been employed by Diamond Light Source (DLS) for beam energy measurements. In this project, we study a new approach to make RSD compatible with user beam operation and provide a continuously updated online measurement. An array of four custom-made scintillation detectors has been installed around the beam pipe, downstream of collimators to capture the highest fraction of lost particles and maximize the count rate. The excitation is gated to half of the stored bunches and the acquisition system counts losses in both halves independently. Using the count in the un-excited part for normalisation suppresses external factors that modify the loss rate. Different parameters of the measurement, like excitation kick strength and duration have been explored to optimise depolarisation and to increase the reliability of the measurement.  
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MOPB17 Using a TE011 Cavity as a Magnetic Momentum Monitor 111
  • J. Guo, J. Henry, M. Poelker, R.A. Rimmer, R. Suleiman, H. Wang
    JLab, Newport News, Virginia, USA
  Funding: Authored by Jefferson Science Associates, LLC with Laboratory Directed Research and Development funding, under U.S. DOE Contract No. DE-AC05-06OR23177.
The Jefferson Lab Electron-Ion Collider (JLEIC) design relies on cooling of the ion beam with bunched electron beam constrained in a pair of long solenoids. The high current cooling electron beam needs to be generated in a magnetized electron source, and the beam's magnetization needs to be maintained during the acceleration and transport to the cooling channel. A non-invasive real time monitoring system is highly desired to quantify electron beam magnetization. The authors propose to use a passive copper RF cavity in TE011 mode as such a monitor. In this paper, we present the mechanism and scaling law of this device, as well as the design and preliminary test results of the prototype cavity.
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MOPC02 Identification of Faulty Beam Position Monitor Based Clustering by Fast Search and Find of Density Peaks 114
  • R. Jiang, Y.B. Leng
    SSRF, Shanghai, People's Republic of China
  • F.Z. Chen, Z.C. Chen, Y.B. Leng
    SINAP, Shanghai, People's Republic of China
  The accuracy and stability of beam position moni-tors(BPMs) are important for all kinds of measurement systems and feedback systems in particle accelerator field. A proper method detecting faulty beam position monitor or monitoring their stability could optimize accel-erator operating conditions. With development in ma-chine learning methods, a series of powerful analysis approaches make it possible for detecting beam position monitor's stability. Here, this paper proposed a clustering analysis approach to detect the defective BPMs. The method is based on the idea that cluster centres are char-acterized by a higher density than their neighbours and by a relatively large distance from points with higher densi-ties. The results showed that clustering by fast search and find of density peaks could classify beam data into dif-ferent clusters on the basis of their similarity. And that, aberrant data points could be detected by decision graph. So the algorithm is appropriate for BPM detecting and it could be a significant supplement for data analysis in accelerator physics.  
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TUOA02 Application of Machine Learning to Beam Diagnostics 169
  • E. Fol, J.M. Coello de Portugal, R. Tomás
    CERN, Geneva, Switzerland
  Machine learning techniques are used in various scientific and industry fields as a powerful tool for data analysis and automatization. The presentation is devoted to exploration of relevant machine learning methods for beam diagnostics. The target is to provide an insight into modern machine learning techniques, which can be applied to improve current beam diagnostics and general applications in accelerators. Possible concepts for future applications are also presented.  
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TUOB02 Optics Measurements in Storage Rings: Simultaneous 3-Dimensional Beam Excitation and Novel Harmonic Analysis 177
  • L. Malina, J.M. Coello de Portugal, J. Dilly, P.K. Skowroński, R. Tomás
    CERN, Geneva, Switzerland
  Optics measurements in storage rings employ turn-by-turn data of transversely excited beams. Chromatic parameters need measurements to be repeated at different beam energies, which is time-consuming. We present an optics measurement method based on adiabatic simultaneous 3-dimensional beam excitation, where no repetition at different energies is needed. In the LHC, the method has been successfully demonstrated utilising AC-dipoles combined with RF frequency modulation. It allows measuring the linear optics parameters and chromatic properties at the same time without resolution deterioration. We also present a new accurate harmonic analysis algorithm that exploits the noise cleaning based on singular value decomposition to compress the input data. In the LHC, this sped up harmonic analysis by a factor up to 300. These methods are becoming a "push the button" operational tool to measure the optics.  
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THOB01 Injection Transient Study Using 6-Dimensional Bunch-by-bunch Diagnostic System at SSRF* 542
  • Y.M. Zhou, Y.B. Leng, N. Zhang
    SSRF, Shanghai, People's Republic of China
  • B. Gao
    SINAP, Shanghai, People's Republic of China
  Beam instability often occurs in the accelerator and even causes beam loss. The beam injection transient process provides an important window for the study of beam instability. Measurement of the bunch-by-bunch dynamic parameters of the storage ring is useful for accelerator optimization. A 6-dimensional bunch-by-bunch diagnostic system has been successfully implemented at SSRF. The measurements of transverse position and size and longitudinal phase and length are all completed by the system. Button BPM is used to measure beam position, phase, and length, and the synchrotron radiation light is used to beam size measurement. Signals are sampled simultaneously by a multi-channel acquisition system with the same clock and trigger. Different data processing methods are used to extract the 6-dimensional information, where the delta-over-sum algorithm for beam position extraction, the Gaussian fitting algorithm for beam size extraction, zero-crossing detection algorithm for beam phase extraction and the two-frequency method for bunch length extraction. The system set up and performance will be discussed in more detail in this paper.  
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-THOB01  
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THOB02 Energy Loss Measurements with Streak Camera at ALBA 548
  • A.A. Nosych, B. Bravo, U. Iriso
    ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
  Analyzing streak camera images of the beam injected into a Storage Ring with no RF voltage allows calculating several parameters, like the energy loss per turn and the energy mismatch between injected and stored beams. These measurements are based on the analysis of the centroid drift path of a bunch as it spirals inwards, changing its rotation period. This drift is clear and measurable in single and multi-bunch modes in several horizontal sweep speeds of the streak. With this technique we also measure the momentum compaction factor and observe its change with respect to the insertion devices' open/closed states. The obtained values are comparable with theoretical expectations, as well as with values measured by other means.  
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THOB03 Long Term Investigation of the Degradation of Coaxial Cables 552
  • M. Kuntzsch, R. Schurig
    HZDR, Dresden, Germany
  • S.J. Burger
    Delta Gamma RF-Expert, Melbourne, Australia
  • T. Weber
    el-spec GmbH, Geretsried, Germany
  For the transport of RF signals coaxial cables with PTFE ('Teflon') as dielectric medium are widely used because they offer a wide bandwidth and low insertion loss. Coaxial cables that are routed in immediate vicinity to the beamline are exposed to ionizing radiation that is mainly generated by beam-loss. In this radiative environment cables change their electrical properties which directly affects the signal on the receiver side and in turn the measured beam parameters. This contribution describes a measurement setup at the superconducting CW accelerator ELBE that was used to investigate the degradation of coaxial cables under well-controlled conditions up to an accumulated dose of 94 kGy. Furthermore the acquired data up to 40 GHz of two coaxial cable samples are presented and the results are discussed.  
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