1. 09-21 Study of bunch length limits Goals: To identify and observe effects which put limits on the minimum bunch length in RHIC. Try to distiguish the limitation coming from resistive wall heating and electron cloud (vacuum, pipe heating) and identify the heat load on the beam pipe from both effects. Benefits: The bunch length of less than 1ns rms value is expected with 56 MHz RF system and in the eRHIC design. In eRHIC smaller bunch length would allow to reach smaller beta* and higher luminosity. The quantative knowledge of the limiting factors will help to better specify the achievable luminosity of eRHIC and to clarify expectations for 56 MHz RF operation at RHIC. V,Ptitsyn, V.N.Litvinenko, C.Montag, S.Y.Zhang

2. Experiment description Inject the proton bunches with intensities about 2-2.5e11. Use 28 MHz RF system with highest possible voltage and, possibly, quad pumping technique in AGS. Slowly approach the RHIC transition to achieve shorter and shorter bunch length and record data on cryo-temperatures, vacuum condition, transverse and longitudinal beam sizes (emittances). To approach the transition two ways will be used (probably, combined): ramping gammaT quads (to oppposite strength than they are used now, and even further, if possible) and slow energy ramp down (so, individual ramp should be created). These measurements have to be done 2 or 3 times with different bunch patterns (to vary the electron cloud production) but maintaining the same n_b*N^2 value (to have the same resistive wall contribution).

3. MeRHIC parameters for e-p collisions not cooledpre-cooledhigh energy cooling pepepe Energy, GeV 2504 4 4 Number of bunches 111 Bunch intensity, 10 11 2.00.312.00.312.00.31 Bunch charge, nC 325 5 5 Normalized emittance, 1e-6 m, 95% for p / rms for e 15736291.57.3 rms emittance, nm 9.4 3.8 0.94 beta*, cm 50 rms bunch length, cm 200.2200.25 beam-beam for p /disruption for e 1.5e-33.13.8e-37.70.0157.7 Peak Luminosity, 1e32, cm -2 s -1 0.932.39.3

5. 09-22 Measurements of the dependence of spin tune on the beam closed orbit Goals: Measure the spin tune shifts caused by several closed orbit effects and compare with theoretical predictions. Benefits: It would help us to establish more accurate tolerances for the orbit control, which are required for the polarization preservation and reproducibility.

6. Experiment Description The experiment implementation will depend on whether the spin flipper is available. With spin flipper we will scan the orbits (that is, change the orbit in steps) in definite locations and measure the spin tune using flipper. Without the flipper we can put the vertical betatron tune closer to a spin resonance (0.75), then vary the orbit until the depolarization is observed. The orbit variation should be done in both (positive and negative) directions to identify the corect spin tune shift. Following orbit variations are considered: 1)Variation of horizontal orbit angle at Snake locations at the injection energy. (This is most important effect). 2)Variation of vertical and horizontal orbit angles at the rotator locations. At the top energy with rotators on. 3)Variation of average radial orbit (by varying RF frequency). At the top energy.

7. Effects of horizontal orbit Siberian Snakes I III IV II -two parts of periodical orbit distortion: closed orbit and average momentum error (non-zero mean orbit) For closed orbit: sn2 sn1 rt1 rt2 For momentum error: measured in Q3-Q4 sectionsmeasured in Q7-Q8 sections Full solution was found: (CA/AP Note 334, M.Bai,V.Ptitsyn, T.Roser) integrates to 0