Progress in the high current experiment (HCX) February-July 2002
This paper reports progress in the HCX experimental program since the last HIF-VNL Program Advisory Committee Review (February 14-15 2002). On July 25 2002 the experiment was shut down for about four weeks to move the control room. A principal area of effort has been to obtain and evaluate the first experimental results carried out with a matched and well-aligned K+ ion beam transported through 10 electrostatic transport quadrupoles. These are the main results and highlights to date: (1) There is no emittance growth within the sensitivity of the diagnostics, and little beam loss. The beam centroid is aligned to within 0.5 mm and 2 mrad of the central axis of the channel, and the envelope mismatch amplitude is <2 mm. (2) A long-life, alumino-silicate source has replaced a contact-ionization source, eliminating depletion induced experimental uncertainties. (3) Significant differences between the experimental data and early theoretical calculations of the beam envelope propagating through the electrostatic quadrupoles were encountered. More detailed envelope models and simulations were developed and experimental parameter sensitivities were analyzed. This work has resolved most of the discrepancy and achievable limits on envelope predictability and control are being probed. (4) The experimental current density distribution, J(x,y), and phase-space data are being used to initialize high-resolution simulations to enable realistic modeling and detailed comparisons to experiment. In other areas of HCX R&D: (1) We have made progress in the development of new time-resolved phase-space diagnostics that will speed up data acquisition in this and other upcoming beam experiments in the HIF-VNL. (2) Preliminary results from a Gas, Electron Source Diagnostic (GESD) are presented, which measures gas desorption and secondary electrons. The secondary emission yield varies as cos-1(q), as predicted theoretically. Data from the GESD will be relevant to upcoming experiments on particle loss and electron effects in a magnetic quadrupole lattice. (3) The design of the superconducting quadrupole cryostat needed for a future phase of HCX experimentation has been refined and a vendor has been selected from a group of five that submitted bids. Construction of an optimized prototype quadrupole began this summer. (4) The design of a longitudinal bunch control induction module is near a final design review (DOE SBIR Phase II). The module will apply agile control of the acceleration waveforms to correct for space charge field effects on the head/tail of the beam.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE Director, Office of Science. Office of Fusion Energy Sciences (US)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 803867
- Report Number(s):
- LBNL-51476; R&D Project: Z46010; B& R AT5015031; TRN: US0300320
- Resource Relation:
- Other Information: PBD: 9 Sep 2002
- Country of Publication:
- United States
- Language:
- English
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