Icfa workshop on diagnostic in high intensity machines october 21 23 2002
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ICFA Workshop on Diagnostic in high-intensity machines – October 21-23, 2002. SNS has all the standard diagnostic necessary for commissioning and low-intensity operation.

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Icfa workshop on diagnostic in high intensity machines october 21 23 2002
ICFA Workshop on Diagnostic in high-intensity machines – October 21-23, 2002

  • SNS has all the standard diagnostic necessary for commissioning and low-intensity operation.

    The goal was to evaluate diagnostic in other machines and understand what are the most relevant devices and methods for measurements at high intensity.

    Tables of Diagnostics used at various machines around the world were generated both for Linacs and Rings.


Diagnostic requiring special treatment for high intensity rings
Diagnostic requiring special treatment for high-intensity rings

General features:

  • Most of diagnostic should cover wide range of intensities as a result of accumulation. Should be capable to produce reliable measurements at high-intensity.

  • Beam loss

  • Beam halo

  • Beam in gap

  • Clearing electrodes, E-detectors

  • Beam profile measurements

  • Incoherent tune measurements


Special diagnostic
Special diagnostic rings

  • Incoherent tune-spread measurements – necessary to understand beam losses at high-intensity operation (several ways of measuring are available, such as

  • Schottky

  • Quadrupole pick-up

  • injection oscillation

  • BTF, etc.

  • Profile measurements: standard WS will have heating problems for high-intensity measurements, IPM can provide desired profiles (Are there any concerns with its operation at high intensity?). Other devices to be considered for high intensity Flying Wire, Luminescence monitor.

  • Halo measurements: essential for understanding beam loss; requires profiles measurements of beam tails 4 orders of magnitude below the peak beam intensity (Scrapers, PLL ?).


Various machines
Various machines rings

Detailed overview of diagnostic was presented for:

FNAL

INR (Russia)

IPNS

GSI

DESY

In addition, there were presentations on

Electron cloud diagnostic, Beam profile measurements, Tune measurements and halo measurements


Incoherent tune measurements
Incoherent tune measurements rings

  • Schottky – used in many machines with unbunched beams:

    a) Concern that will not work effectively for bunched beams due to a large coherent signal.

    b) Most likely will not work during accumulation.

  • Indirect method by measuring quadrupole mode depressed by space charge. Requires quadrupole kicker and quadrupole monitor (IPM capture quadrupole oscillations as well). This method was recently demonstrated at CERN, GSI and Japan.

  • Other methods such as BTF, etc. were presented by Pete Cameron and are being evaluated for the SNS ring.


Profile measurements
Profile measurements rings

  • IPM – does not work as a reliable diagnostic in almost all machines – profiles are not predictable and can be from 20% to factor of 2-3 off. General agreement with Roger C. that this may be due to the fact that they collect ions and absence of external magnetic fields.

    RHIC/SNS IMP collects electrons in external magnetic field which perhaps solved the problems of other IPM. General agreement – very useful device, if it is working.

    2. Luminescent Monitors/ Gas scintillation – extensively used at other accelerator. Beam profile is typically 20 % wider

    3. Some new ideas are being tried like vibrating wire scanner, temperature of wires, etc.


Halo measurements
Halo measurements rings

  • LEDA halo measurements

    a) Does not look like the agreement with theory was established.

    b) It is stated that that the device WS+Scraper measures halo at 1*10^-5 level with very good accuracy. However data in the tails of measured distribution is scattered from 10^-5 to 10^-4 level.

    c) No new data was presented. Last experiments were done a year ago. No new experiments are expected.

    d) Device is suitable for low energy measurements , not like GeV in Ring.

    2. Actually, other halo measurements done in high-intensity transport (UMCP, LBL, Saclay) were not presented.


Halo measurements1
Halo measurements rings

3. DESY: Counting technique is a very accurate way to measure halo.

In experiments – halo was measured to 10^-4 - 10*-5 level, can go to 10^-6 (1000000:1) level.

4. Pete Cameron presented several ideas for halo measurements at AGS.

Electron collectors:

Different effectiveness of electron collectors for machines with short bunches and long bunches was reported (B-factory: 8% helped a lot, PSR: 15% - not a big effect).


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