THZBB —  Thursday Parallel Session 6   (05-Sep-19   14:00—16:00)
Chair: S.H. Kim, FRIB, East Lansing, Michigan, USA
Paper Title Page
Commissioning of the FRIB Beam Instrumentation  
  • S.M. Lidia
    FRIB, East Lansing, Michigan, USA
  A large variety of beam instrumentation have been developed, installed and commissioned. This talk will present various aspects of physics and engineering of beam instrumentation devices and their performance during the beam commissioning.  
slides icon Slides THZBB1 [20.507 MB]  
Single-Shot Wakefield Measurement System  
  • Q. Gao
    TUB, Beijing, People’s Republic of China
  A new experimental technique for the accurate measurements of wakefields is presented. Knowledge of wakefields is required for many applications ranging from the suppression of wakefields that arise from geometrical discontinuities to the enhancement of wakefields in structure and plasma based wakefield accelerators. In the past, direct measurements of wakefields were done with the drive-witness technique wherein the delay of a short witness beam trailing collinearly behind a high-charge drive beam is scanned over multiple shots and the wakefield is inferred from the energy spectrum of the witness beam. That technique is limited by shot-to-shot jitter, overlap of the drive and witness energy spectrum and the loss of all time-domain information. In this paper, we describe a new technique that overcomes these limitations by measuring the longitudinal phase space of a long witness beam and the drive beam in a single shot. We conclude by presenting experimental results to demonstrate its feasibility using a dielectric structure wakefield accelerator.  
slides icon Slides THZBB2 [4.070 MB]  
THZBB3 Novel Emittance Measurement Combining Foil Focusing and Pepper-Pot Techniques -1
  • K.A. Schultz, G.T. Ortiz, M.E. Schulze
    LANL, Los Alamos, New Mexico, USA
  • C. Carlson, D. Guerrero
    NSTec, Los Alamos, New Mexico, USA
  Funding: Work supported by the US National Nuclear Security Agency and the US Department of Energy under contract DE-AC52-06NA25396.
In this paper, we describe a direct measurement of foil focusing of an intense, relativistic electron beam com-bined with the pepper-pot technique to perform emit-tance measurements. Foil focusing occurs when a thin, grounded, conducting foil shorts out the radial electric field of a transiting electron beam, causing its self-magnetic field to focus the beam. A 40-ns pulse was extracted from the main pulse of the 16-MeV, 1.65 kA beam from Axis-II of the Dual Axis Radiographic Hy-drodynamic Test Facility to perform the measurements. We show that not accounting for foil focusing signifi-cantly reduces the measured emittance.
slides icon Slides THZBB3 [5.379 MB]  
THZBB4 Beam Loss in the First Segment of the FRIB Linac -1
TUPLE17   use link to see paper's listing under its alternate paper code  
  • R. Shane, S. Cogan, S.M. Lidia, T. Maruta
    FRIB, East Lansing, Michigan, USA
  Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661.
Beam loss in accelerators is an unavoidable and often unwanted reality, but it is not without its use. Information from beam loss can be leveraged to optimize the tune and improve beam quality, in addition to monitoring for machine fault and failure conditions. The folded geometry at the Facility for Rare Isotope Beams (FRIB) presents a unique challenge in the detection of radiative losses, resulting in the introduction of non-traditional measurement schemes. In addition to neutron detectors and pressurized ionization chambers, FRIB will utilize halo ring monitors, fast thermometry within the cryomodules, and differential beam-current measurements. This paper will present an analysis of beam-loss measurements from commissioning the first segment of the FRIB accelerator, and a discussion of ways to evaluate and monitor the health of the beam loss monitoring system.
slides icon Slides THZBB4 [2.473 MB]  
THZBB5 Present Status and Upgrades of the SNS Ion Beam Bunch Shape Monitors -1
  • V. Tzoganis, A.V. Aleksandrov, R. Dickson
    ORNL, Oak Ridge, Tennessee, USA
  Six interceptive Feschenko-style longitudinal bunch profile monitors have been deployed in the normal conducting part of the SNS linac and HEBT. They have been operational for more than 10 years and although their performance has been satisfactory, reliability and parts obsolescence must be addressed. The upgrade plan focuses in mainly two areas, electronics architecture modernization and improvement of measurement resolution. In the first phase that is presented here the objective is to improve the control and readout electronics taking advantage of more recent technology. This will primarily address the obsolescence issues with older components, the frequent RF power failures, the non-trivial maintenance and troubleshooting and will lead to a simpler and more reliable system. This contribution describes in detail the implemented upgrades and presents the first experimental data.  
slides icon Slides THZBB5 [4.931 MB]  
Error Minimization in Transverse Phase-Space Measurements Using Quadrupole and Solenoid Scans  
SUPLO03   use link to see paper's listing under its alternate paper code  
TUPLE18   use link to see paper's listing under its alternate paper code  
  • C.Y. Wong
    NSCL, East Lansing, Michigan, USA
  • S.M. Lund
    FRIB, East Lansing, Michigan, USA
  Quadrupole and solenoid scans are common techniques where a series of beam profile measurements are taken under varying excitation of the linear focusing elements to unfold second-order phase-space moments of the beam at an upstream location. Accurate knowledge of the moments is crucial to machine tuning and understanding the underlying beam dynamics. The scans have many sources of errors including measurement errors, field errors and misalignments. The impact of these uncertainties on the moment measurement is often not analyzed. This study proposes a scheme motivated by linear algebra error bounds that can efficiently select a set of scan parameters to minimize the errors in measured initial moments. The results are verified via a statistical error analysis. These techniques are being applied at the Facility for Rare Isotope Beams (FRIB). We find that errors in initial moments can be large under conventional scans but are greatly reduced using the procedures described.  
slides icon Slides THZBB6 [2.150 MB]