Search Results (14 total)

Using a movable Schottky cavity resonant at 2.07 GHz, we have developed a simple method of deriving the beam sizes at the detector. In this report we will explain the theory behind the method, describe the system and the signal processing, and then present the results from experiments using this method. We will also present our plans for using this new technique for obtaining beam emittances during normal operation of the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL).

Errors in delivering a uniformly distributed radiation dose to biological and material samples exposed to charged particle beams are a significant problem for experimenters. In this paper, we discuss data collected on the uniform beam distributions produced for NASA’s Space Radiation Laboratory (NSRL) at Brookhaven National Laboratory (BNL), using a method that was conceived theoretically and tested experimentally at BNL. This method [N. Tsoupas , Nucl. Sci. Eng. 126, 71 (1997)] of generating uniform beam distributions on a plane normal to the beam’s direction relies only on magnetically focusing the transported beam; no collimation of the beam is required or any other type of interaction of the beam with materials other than the target material. The method compares favorably with alternative methods of producing such distributions, and it can be applied to the entire energy spectrum of charged particle beams that are delivered to the NSRL’s experiments by the Booster for the Alternating Gradient Synchrotron at BNL.

An 11.4% partial Siberian snake was used to successfully accelerate polarized protons through a strong intrinsic depolarizing spin resonance in the Alternating Gradient Synchrotron (AGS). No noticeable depolarization was observed. This opens up the possibility of using a 20% to 30% partial Siberian snake in the AGS or other medium energy proton synchrotrons to overcome all weak and strong depolarizing spin resonances.

In order to further understand phenomena observed during studies of adiabatic excitation of longitudinal bunch shape oscillations [M. Bai et al., Phys. Rev. ST Accel. Beams 3, 064001 (2000)], we have developed a simulation using a one-turn map. In this report we will present the physical foundations for the simulation and the methods used in the simulator. We will present simulation results using parameters of actual experiments, along with the corresponding experimental results.

Response is made to J. A. MacLachlan's preceding Comment [Phys. Rev. ST Accel. Beams 4, 017001 (2001)]. We are gratified to see that high quality simulations, as presented by MacLachlan, verify our experimental results.

By modulating the rf voltage at near twice the synchrotron frequency, the longitudinal bunch shape can be modulated. This method can be used to shorten bunches. We show experimentally that the bunch shape can be modulated while preserving the longitudinal emittance when the rf voltage modulation is turned on adiabatically. Experimental measurements will be presented along with theoretical predictions.

A 9° solenoidal spin rotator or 5% partial Siberian Snake was used to successfully accelerate polarized protons for the first time to 10.8 GeV kinetic energy in the Brookhaven Alternating Gradient Synchrotron with partial depolarization due to the intrinsic resonance crossing. It was found that a 5% partial snake can effectively overcome 18 imperfection resonances in this energy range. We also observed an interference between the spin flip induced by an intrinsic resonance and linear coupling due to the solenoid field of the partial snake.

We measured the analyzing power A out to P_⊥²=7.1 (GeV/c)² with high precision by scattering a 24-GeV/c unpolarized proton beam from the new University of Michigan polarized proton target; the target’s 1-W cooling power allowed a beam intensity of more than 2×10¹¹ protons per pulse. This high beam intensity together with the unexpectedly high average target polarization of about 85% allowed unusually accurate measurements of A at large P_⊥². These precise data confirmed that the one-spin parameter A is nonzero and indeed quite large at high P_⊥²; most theoretical models predict that A should go to zero.

Accelerating polarized protons to 22 GeV/c at the Brookhaven Alternating Gradient Synchro- tron required both extensive hardware modifications and a difficult commissioning process. We had to overcome 45 strong depolarizing resonances to maintain polarization up to 22 GeV/c in this strong-focusing synchrotron. At 18.5 GeV/c we measured the analyzing power A and the spin-spin correlation parameter A_nn in large- P_⊥² proton-proton elastic scattering, using the polarized proton beam and a polarized proton target. We also obtained a high-precision measurement of A at P_⊥²=0.3 (GeV/c)² at 13.3 GeV/c. At 18.5 GeV/c we found that A_nn=(-2±16)% at P_⊥²=4.7 (GeV/c)², where it was about 60% near 12 GeV at the Argonne Zero Gradient Synchrotron. This sharp change suggests that spin-spin forces may have a strong and unexpected energy dependence at high P_⊥².

We measured the analyzing power A and the spin-spin correlation parameter A_nn in medium-P_⊥² proton-proton elastic scattering, using a polarized-proton target and the 18.5-GeV/c Brookhaven Alternating-Gradient Synchrotron polarized-proton beam. We found sharp dips in both A and A_nn, which occur at different P_⊥² values. The unexpected sharp structure in the spin-spin force occurs near P_⊥²=2.3 (GeV/c)² where the elastic cross section has no apparent structure.

We measured the analyzing power A and the spin-spin correlation parameter A_nn, in large-P_⊥² proton-proton elastic scattering, using a polarized-proton target and the polarized-proton beam at the Brookhaven Alternating-Gradient Synchrotron. We also used our polarimeter to measure A at small P_⊥² at 13 GeV with good precision and found some deviation from the expected 1 / P_lab behavior. At 18.5 GeV/c we found A_nn=(-2±16)% at P_⊥²=4.7 (GeV/c)². Comparison with lower-energy data from the Argonne Zero-Gradient Synchrotron shows a sharp and surprising energy dependence for A_nn at large P_⊥².

The spin analyzing power A in 28-GeV/c proton-proton elastic scattering was measured at P_⊥ ²=6.5 (GeV/c)² using a polarized proton target and a high-intensity unpolarized proton beam at the Brookhaven National Laboratory Alternating Gradient Synchrotron. The result of (24±8)% confirms that the analyzing power is large and rising in the large-P_⊥ ² region.

Using the new Brookhaven Alternating Gradient Synchrotron polarized proton beam and our polarized proton target, we measured the spin-spin correlation parameter A_nn in 16.5-GeV/c proton-proton elastic scattering. We found an A_nn of (6.1±3.0)% at P_⊥ ²=2.2 (GeV/c)². We also measured the analyzing power A in two independent ways, providing a good test of possible experimental errors. Comparing our new data with 12-GeV Argonne Zero Gradient Synchrotron data shows no evidence for strong energy dependence in A_nn in this medium-P_⊥ ² region.