FY 2006 AGS Polarized Proton Run Plan

January 13, 2006

Haixin Huang

Environment: According to the current schedule, which is subject to change, AGS pp setup will start on January 16. We have about three weeks running time before RHIC setup work starts which essentially will take away the injector setup for one week before the store can be established. Given the past experience that we will have a long commissioning time for the AGS pp setup, we are going to run two shifts per day with the operators' help in owl shifts. To prepare for that, we need detail and easy-to-understand instructions and recipes before run starts. Our goal is to establish polarization and intensity required for RHIC around February 6. We will start with 15% cold snake and 5.9% warm snake.

 

General Objectives:

 

Establish an injector setup providing protons with polarization about 65% (or “as high as possible”) and ≥1.4*10^11/bunch at Gγ = 46.5 (or 45.5, depends on the results of field scan). We expect to deliver 65% polarization to RHIC in about three weeks.

 

Plans

Machine parameters:
ν_x=8.70, ν_y>8.90 at injection and ramp up to 8.96 or higher after Gγ = 7.5.
transverse emittance 10π (95% normalized); longitudinal emittance <0.8eV-s.
warm snake current=2670A.(8.5% at injection, 5.9% at extraction).
cold snake helix current=282A and solenoid current=212A. (22.2% at injection, 14% at extraction).
AGS rep rate=1.3-2.5 sec(shorter one for machine setup and the longer one for polarization measurement).
The injection and extraction energies: Gγ = 4.5 and Gγ = 46.5 (or 45.5), respectively.
Setup Before Snake On

  • We need two main magnet functions: one with dwell field only and the other ramping to extraction energy. Establish beam for both machine and archive them.
  • Establish beam in the Booster then AGS (injection at Gγ=4.5, full energy ramp,Gγ = 46.5 (rf on) without snake on. [3 shifts]
  • Beta function measurement by varying single corrector around the AGS ring with snakes off. [1 shifts]
  • Turn on the snake compensation quads and measure tunes before and after they are on. Turn on the snake orbit bumps (with different set values) to check with model. [1 shifts]
  • Commissioning other instrumentations: new AGS tune-meter; IPM (with higher high voltage). [0-1 shift]
  • E880 polarimeter setup. This is expected to be done by a separated crew and most work can be done in parallel with other activities. [0-1 shift].
  • Harmonics corrections in Booster for both =3 and 4, sine and cosine. This should be done at injection energy and without energy ramp. The data taking is much faster this way. If the harmonics corrections from last year produce polarization around 80%(asymmetry 65*10^-3), the full harmonics scan can be delayed to later time. [1-2 shifts]
  • CNI polarimeter commissioning. We have several upgrades this year: faster readout, horizontal targets and 45 degree detectors. So expect longer commissioning time. The setup can start as soon as beam survives at extraction energy. Prior to this work, the orbits (both horizontal and vertical) at top energy in C15 section should be set as flat (both in time and angle) as possible. Polarization level is preferred to be zero for this stage but not necessarily. Since this involves different crew, it can be done in parallel with other activities. [4 shifts].

  • Setup with Both Snakes on
  • The goal is to dial in all predicted values for compenstation quads and bumps with both snakes on. Start with on-demand mode and intensity of a few 10^10. Turn on cold snake (helical 282A, solenoid 212A,trim1 0A, trim2 7A) and E20 warm snake (2670A). Turn on correction quads and bumps(functions are under development) for both snakes. While tuning the injection beam survival(first with rf off, then rf on), the beam dump bump (J10) should be on at injection porch. After reaching a few times 10^10 beam survives, remove the dump bump and tune for beam survival along the ramp.
  • 1. Tune the AGS injection to maximize beam survive at injection.
    2. Correct both horizontal and vertical orbits with iterations.
    3. Tune the 8th and 9th harmonics along the ramp.
    4. Start with vertical tune around 8.8 along the ramp.
    5. Raise vertical tunes along the ramp while tuning the orbit. The vertical tune should be chosen to avoid the higher order snake resonances, especially at 36+ν. The porposed vertical tune values are: 0+ν (~8.96 or higher), 12+ν (~8.97) , 36-ν(8.98) and 36+ν(8.985).
    6. Measure polarization at extraction.
    [6-8 shifts]
  • If having difficulty to reach high polarization with close to 10^11 bunch intensity, the backup plan is to use ac dipole with warm snake only. The manet function needs to be Gγ=46.5 in this case.The following work in this section will be skipped until AGS extraction work is done. [6 shifts]
  • Measure polarization at extraction as function of B field. The field scan should cover Gγ = 44.5 to 47. [3 shifts]
  • Measure dispersion and aperture at injection with both snakes on. [1 shift]
  • Increase intensity from source gradually to the desired intensity. Measure polarization as intensity goes up. [2 shift]
  • Measure polarization at extraction as function of various quantities. There are several potential causes for polarization loss and they need to be scanned: [4 shifts]
  • 1. 9th harmonics in the early part of the ramp.
    2. Vertical tune not high enough before 0+ν.
    3. Vertical tune not high enough at 0+ν (high order snake resonance).
    4. Vertical tune not high enough at 36+ν (high order snake resonance).
    5. Vertical tune not high enough at 48-ν.
  • Beta function measurement by varying single corrector around the AGS ring with both snakes on. [1 shifts]

  • Low Energy Polarization Check
  • Check polarization at Gγ=7.5 and 12.5. [2 shifts]
  • Calibrate E880 polarimeter with forward arms at Gγ=4.5. This would require heavy scraping to get small beam size. [2 shifts]

  • Setup Extraction
  • Extraction bump and synchro setup. [2 shifts]
  • Measure polarization after the bump and synchro are established. [1 shift]
  • Set up AtR line (up to W dump) if Gγ=45.5 extraction energy is chosen.[1 shift]
  •  

    RF Setup at Extraction
  • RF group requests about 5 shifts (not consecutive) to reduce longitudinal emittance and achieve better match at AtR. [5 shifts]

    Expect to reach 65% polarization (with 80% as input) and 1.4*10^11 intensity. If this goal is reached, then the remaining time will be divided into two parts: maintaining polarized beam for RHIC injection, and AGS study.

     

    AGS study agenda (more to be added)
    1. explore the horizontal resonance at flattop with enlarged horizontal emittance (B-field scan). Small tune spread beam is preferred.
    2. explore relation of  intensity vs. polarization, such as comparing polarization measured with wide and narrow targets; studying prompt effect(need to record raw signals as special run).
    3. Study radial component due to strong snake.
    4. Study both vertical and horizontal polarization profiles.
    5. Beta function measurement by varying single corrector around the AGS ring with snakes on and off.
    6. 1/2 integer correctors to reduce beam loss when tune is very close to 9.

     

     

    AGS pp Operation System Experts


    Booster scraping: Keith
    BtA lattice: Keith, Nick, Woody
    AGS/Booster optics control application: Kip, Kevin
    AGS injection tuning: Keith, Leif, Woody
    AGS RF: Keith, KevinS
    AGS new tune-meter: Mei, Leif
    AGS old tune-meter: Leif
    AGS IPM: Haixin,Kevin
    AGS orbit control and display: Leif, Woody
    Data spreadsheet: Waldo
    AGS snake operation: Haixin, Leif
    Snake bumps and corrections: Nick, Leif, Alfredo
    AGS E880 polarimeter: Haixin
    AGS CNI polarimeter: Kin, Haixin, Sandro
    AGS extraction: Nick, Woody
    AGS AC dipole: Mei
    AGS lattice matching: Alfredo, Nick