STUDIES OF ENERGY RECOVERY LINACS AT ... - CASA
STUDIES OF ENERGY RECOVERY LINACS AT ... - CASA STUDIES OF ENERGY RECOVERY LINACS AT ... - CASA
FIG. 2.11: A 3-wire scanner oriented at 45 ◦ with respect to the horizontal plane. In order to get sufficient resolution of the beam sizes, the horizontally focusing quadrupole at 2L21 was scanned to extract the horizontal emittance and the verti- cally focusing quadrupole at 2L22 was scanned to extract the vertical emittance. A 3-wire scanner - installed approximately 30 cm upstream of the dipole magnet used to deflect the energy recovered beam to the dump - was used to measure beam sizes. An actuator drives the wire scanner which is mounted at an angle of 45 ◦ with respect to the horizontal axis. Using a 3-wire scanner (to measure x, x-y, y profiles) each scan yielded six distinct peaks (3 wires × 2 beams). Initially, there was some con- cern as to how to differentiate each peak and assign them to the appropriate beam. However it soon became clear that the energy recovered beam (56 MeV or 20 MeV, depending on the injector setup) did not produce nearly as high, sharp peaks as the accelerated beam (1056 MeV or 1020 MeV). This fact was easily confirmed by using dipole correctors to locally steer the beam and identifying the displaced peaks with the lower energy beam. A typical scan is shown in Fig. 2.12. Because the capabil- ity to automatically extract beam sigmas from the wire scans did not exist at the 41
FIG. 2.12: A typical wire scan near the extraction region showing six distinct peaks as a result from a 3-wire scanner passing through two co-propagating beams. time of the experiment, analysis was performed off-line. This resulted in unforeseen difficulties which will be discussed in Section 2.4.3. The data analysis program Igor Pro [40] was used to analyze the raw wire scans. The program has the feature that only regions selected by the user are used for curve-fitting. This is convenient for the wire scans since there are multiple peaks and also because there is the possibility of peaks which are partially merged. The program applies a Gaussian fit to the data of the form y(x) = A √ 2πσ e − x−B √ 2σ 2 42 (2.14) To account for the effect of the 45 ◦ angle of the wire scanner on the x and y profiles (the x-y profile requires no correction) the extracted sigmas are divided by a factor of √ 2.
- Page 9 and 10: ACKNOWLEDGMENTS First and foremost
- Page 11 and 12: 6.1 Summary of the measured effects
- Page 13 and 14: 2.10 Illustration of quadrupole sca
- Page 15 and 16: 5.1 Successive frames in time (prog
- Page 17 and 18: 6.8 A plot of 1/Qeff versus average
- Page 19 and 20: ABSTRACT An energy recovering linac
- Page 21 and 22: CHAPTER 1 Introduction An increasin
- Page 23 and 24: FIG. 1.1: Schematic of a generic li
- Page 25 and 26: FIG. 1.2: A CEBAF 5-cell cavity wit
- 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: eams. The effects of varying the qu
- 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 and 78: FIG. 2.19: The GASK signal measured
- Page 79 and 80: FIG. 2.20: The measured normalized
- 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
FIG. 2.11: A 3-wire scanner oriented at 45 ◦ with respect to the horizontal plane.<br />
In order to get sufficient resolution of the beam sizes, the horizontally focusing<br />
quadrupole at 2L21 was scanned to extract the horizontal emittance and the verti-<br />
cally focusing quadrupole at 2L22 was scanned to extract the vertical emittance. A<br />
3-wire scanner - installed approximately 30 cm upstream of the dipole magnet used<br />
to deflect the energy recovered beam to the dump - was used to measure beam sizes.<br />
An actuator drives the wire scanner which is mounted at an angle of 45 ◦ with respect<br />
to the horizontal axis. Using a 3-wire scanner (to measure x, x-y, y profiles) each<br />
scan yielded six distinct peaks (3 wires × 2 beams). Initially, there was some con-<br />
cern as to how to differentiate each peak and assign them to the appropriate beam.<br />
However it soon became clear that the energy recovered beam (56 MeV or 20 MeV,<br />
depending on the injector setup) did not produce nearly as high, sharp peaks as the<br />
accelerated beam (1056 MeV or 1020 MeV). This fact was easily confirmed by using<br />
dipole correctors to locally steer the beam and identifying the displaced peaks with<br />
the lower energy beam. A typical scan is shown in Fig. 2.12. Because the capabil-<br />
ity to automatically extract beam sigmas from the wire scans did not exist at the<br />
41
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