Experimental Evidence of the 90° Stop Band in the GSI UNILAC

The envelope instability of high intensity beams in circular accelerators is studied via multiparticle simulations. The space charge kicks are derived from a Gaussian potential model for an efficient tracking. The evolution of the envelope phase space coordinates are derived from the bunch distribution. We found that the envelope stop band played an important role in emittance growth. Correction schemes of the envelope stop bands are studied. Because the space charge force pushes the envelope tunes downward, harmonics less than twice the betatron tunes are also important on emittance growth. Our code is efficient and fast, it can be used to study the effect of space charge force on high power accelerators.

Section: Introductionmentioning

confidence: 99%

Simulations of beam envelope dynamics in circular accelerators

Chao

Lee

2015

“…[mrad] more complex beam lines even with strong space charge [20,21]. The beam moments at the doublet entrance also can be measured if a pepper-pot device will be installed right behind the last singulet.…”

Section: Beams To Be Strippedmentioning

confidence: 99%

Concept for controlled transverse emittance transfer within a linac ion beam

Groening

2011

Self Cite

For injection of beams into circular machines with different horizontal and vertical emittance acceptance, the injection efficiency can be increased if these beams are flat, i.e., if they feature unequal transverse emittances. Generation of flat electron beams is well known and has been demonstrated already in beam experiments. It was proposed also for ion beams that were generated in an electron-cyclotronresonance (ECR) source. We introduce an extension of the method to beams that underwent charge state stripping without requiring their generation inside an ECR source. Results from multiparticle simulations are presented to demonstrate the validity of the method.

“…Many halo generation mechanisms have been studied such as space charge coupling resonances [2], mismatch [3], envelope instability [4], etc. Recently it is discovered that a fourth order space charge resonance 4 ¼ 360 is excited in high intensity linear accelerators, practically replacing the envelope instability when depressed phase advance per cell is close to 90 [5] and experimentally confirmed [6].…”

Section: Introductionmentioning

confidence: 97%

Evidence of a halo formation mechanism in the Spallation Neutron Source linac

Jeon

2013

Phys. Rev. ST Accel. Beams 5, 094201 (2002)] are verified experimentally through a series of emittance measurements performed during the drift tube linac tank 1 commissioning of the Spallation Neutron Source. This is a rare experiment evidence of a halo formation mechanism. As the simulation predicts, the emittance measurements clearly show a visible halo reduction as well as a significant rms emittance reduction when the proposed round beam optics is employed. The emittance measurement results are consistent with multiparticle simulations and also consistent with wire scanner results. These measurements serve as a valuable code benchmarking for a beam under an intense space charge effect.