STUDIES OF ENERGY RECOVERY LINACS AT ... - CASA
STUDIES OF ENERGY RECOVERY LINACS AT ... - CASA STUDIES OF ENERGY RECOVERY LINACS AT ... - CASA
Upgrade the ratio is approximately 20:1. With the injector set to provide 56 MeV into the linac, 80 µA of cw beam, ac- celerated to 1056 MeV and energy recovered at 56 MeV, was steered to the energy recovery dump. Electron source problems, and not issues related to the energy re- covery process, limited operation to below the typical 100 µA average beam current. Changing the injection energy to 20 MeV, 1 µA of cw beam was energy recovered, after being accelerated to 1020 MeV. The low average current does not represent a fundamental limit, rather it reflects the lack of time available to optimize the ma- chine for handling the increased beam losses observed at this lower injection energy. An understanding of how the emittance evolves can be gained by making mea- surements at several locations in the machine. The results for the two machine configurations, Einj = 56 MeV and Einj = 20 MeV, are summarized in Fig. 2.20 and Fig. 2.21, respectively. The arc 2 emittance data in Fig. 2.20 has been removed for reasons discussed in Section 2.4.5. Qualitatively, the emittances for each machine configuration evolve in a similar manner. Moreover, it can be concluded that the process of energy recovery does not degrade the transverse emittance, since the emit- tance growth on the accelerating pass is consistent with the growth on the energy recovery (decelerating) pass. Quantifying beam loss is vital for the next generation of ERLs which propose to operate with megawatt beam powers and where even small amounts of beam loss can severely damage machine components. While the beam loss in CEBAF-ER was not measured directly, an upper limit of 0.5 µA can be used due to the fact that a stable machine configuration with 80 µA of cw beam was established and did not cause machine trips due to the beam loss accounting system. As a result, the beam loss in CEBAF-ER is comparable to the beam loss in standard CEBAF operations [36]. A summary of beam loss in the FEL Demo, CEBAF and CEBAF with energy recovery is given in Table 2.6. 59
FIG. 2.20: The measured normalized transverse emittance at various locations in CEBAF for the Einj = 56 MeV configuration. FIG. 2.21: The measured normalized transverse emittance at various locations in CEBAF for the Einj = 20 MeV configuration. 60
- Page 27 and 28: The solution to Eq. (1.3) is U(t) =
- Page 29 and 30: y reducing the impedance of HOMs, a
- Page 31 and 32: Despite its success, this method of
- Page 33 and 34: design parameters, most notably ach
- Page 35 and 36: 1.4.2 Machine Optics The second cat
- Page 37 and 38: analytic model elucidates many impo
- Page 39 and 40: CHAPTER 2 CEBAF with Energy Recover
- Page 41 and 42: FIG. 2.1: Energy versus average cur
- Page 43 and 44: FIG. 2.3: Additional hardware insta
- Page 45 and 46: FIG. 2.4: A picture of the energy r
- Page 47 and 48: dipoles and beam diagnostics such a
- Page 49 and 50: FIG. 2.7: Horizontal (red) and vert
- Page 51 and 52: FIG. 2.8: Illustration of the cryom
- Page 53 and 54: linac and θNL is the RF phase. The
- Page 55 and 56: 2.4 Transverse Emittance One of the
- Page 57 and 58: where σ2 is the rms beam size meas
- Page 59 and 60: eams. The effects of varying the qu
- Page 61 and 62: FIG. 2.12: A typical wire scan near
- Page 63 and 64: quadratic fit and a multiple regres
- Page 65 and 66: ting the data is difficult. Without
- Page 67 and 68: primary source of error is measurin
- Page 69 and 70: identified, although the phase dela
- Page 71 and 72: TABLE 2.3: Comparison of Twiss para
- Page 73 and 74: the results of the fits. The vertic
- Page 75 and 76: FIG. 2.18: Schematic illustrating t
- Page 77: FIG. 2.19: The GASK signal measured
- Page 81 and 82: CHAPTER 3 The Jefferson Laboratory
- Page 83 and 84: FIG. 3.1: Schematic of the 10 kW FE
- Page 85 and 86: FIG. 3.2: Layout of the DC photocat
- Page 87 and 88: accelerating gradient at the front
- Page 89 and 90: eason for making the endloops achro
- Page 91 and 92: FIG. 3.7: Illustration of path leng
- Page 93 and 94: 3.5 Longitudinal Dynamics This sect
- Page 95 and 96: FIG. 3.9: The effect of a thin focu
- Page 97 and 98: Under the constraint that each orde
- Page 99 and 100: form of beam breakup not only occur
- Page 101 and 102: 4.1 The Pillbox Cavity Although the
- Page 103 and 104: FIG. 4.2: Electric field (red) and
- Page 105 and 106: where the full 4×4 transfer matrix
- Page 107 and 108: The threshold is inversely proporti
- Page 109 and 110: 4.3 BBU Simulation Codes: Particle
- Page 111 and 112: 6. The second pass beam bunch then
- Page 113 and 114: which excites it. The BBU instabili
- Page 115 and 116: Equation (4.41) is a dispersion rel
- Page 117 and 118: FIG. 4.4: Output from MATBBU showin
- Page 119 and 120: FIG. 4.5: Setup for measuring cavit
- Page 121 and 122: Consequently, depending on the exte
- Page 123 and 124: The projection of the beam displace
- Page 125 and 126: TABLE 4.1: Experimental measurement
- Page 127 and 128: FIG. 4.10: A plot showing the effec
FIG. 2.20: The measured normalized transverse emittance at various locations in CEBAF<br />
for the Einj = 56 MeV configuration.<br />
FIG. 2.21: The measured normalized transverse emittance at various locations in CEBAF<br />
for the Einj = 20 MeV configuration.<br />
60