1 | <head> |
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2 | <title>RFCAVITY</title> |
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3 | <!-- Changed by: Chris ISELIN, 27-Jan-1997 --> |
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4 | <!-- Changed by: Hans Grote, 30-Sep-2002 --> |
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5 | </head> |
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6 | |
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7 | <body bgcolor="#ffffff"> |
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8 | |
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9 | <center> |
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10 | EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH |
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11 | <IMG SRC="http://cern.ch/madx/icons/mx7_25.gif" align=right> |
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12 | <h2>RF Cavity</h2> |
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13 | </center> |
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14 | |
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15 | <pre> |
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16 | label: RFCAVITY, L=real,VOLT=real,LAG=real,HARMON=integer,FREQ=real; |
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17 | <!-- HARMON=integer, BETRF=real,PG=real, |
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18 | FREQ=real,SHUNT=real,TFILL=real; --> |
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19 | </pre> |
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20 | An RFCAVITY has eight real attributes and one integer attribute: |
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21 | <ul> |
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22 | <li>L: |
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23 | The length of the cavity (DEFAULT: 0 m) |
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24 | <li>VOLT: |
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25 | The peak RF voltage (DEFAULT: 0 MV). |
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26 | The effect of the cavity is |
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27 | <p> |
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28 | delta(<i>E</i>) = VOLT * sin(2 pi * (LAG - HARMON * <i>f<sub>0</sub> t</i>)). |
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29 | <p> |
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30 | <li>LAG: |
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31 | The phase lag [2pi] (DEFAULT: 0). |
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32 | <li>FREQ: |
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33 | The frequency [MHz] (no DEFAULT). |
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34 | Note that if the RF frequency is not given, it is |
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35 | computed from the harmonic number |
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36 | and the revolution frequency <i>f<sub>0</sub></i> as before. However, |
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37 | for accelerating structures this makes no sense, |
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38 | and the frequency is mandatory. |
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39 | <li>HARMON: |
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40 | The harmonic number <i>h</i> (no DEFAULT). Only if the frequency is not given. |
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41 | <!-- <li>BETRF: |
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42 | RF coupling factor (DEFAULT: 0). |
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43 | <li>PG: |
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44 | The RF power per cavity (DEFAULT: 0 MW). |
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45 | <li>SHUNT: |
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46 | The relative shunt impedance (DEFAULT: 0 MOhm/m). |
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47 | <li>TFILL: |
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48 | The filling time of the cavity T<sub>fill</sub> |
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49 | (DEFAULT: 0 microseconds). --> |
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50 | <li><font color=ff0000><i> Please take note, that the following |
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51 | MAD8 attributes: BETRF, PG, SHUNT and TFILL are currently not |
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52 | implemented in MAD-X!</i>< |
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53 | <li><i> Note as well that twiss is 4D only. As a consequence the TWISS |
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54 | parameters in the plane of non-zero dispersion may not close as |
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55 | expected. Therefore, it is best to perform TWISS in 4D only, i.e. with |
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56 | cavities switched off. If 6D is needed one has to use the |
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57 | <a href="../ptc_twiss/ptc_twiss.html">ptc_twiss</a> command. |
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58 | </i></font> |
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59 | </ul> |
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60 | |
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61 | The RFCAVITY has attributes that will only become active in PTC: |
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62 | <ul> |
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63 | <li>n_bessel (DEFAULT: 0): <p> |
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64 | Transverse focussing effects are typically ignored in the cavity in |
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65 | MAD-X or even PTC. This effect is being calculated to order n_bessel, |
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66 | with n_bessel=0 disregarding this effect and with a correct treatment |
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67 | when n_bessel goes to infinty. |
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68 | <li>no_cavity_totalpath (DEFAULT: no_cavity_totalpath=false):<p> |
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69 | flag to choose if in a cavity the transit time factor is considered |
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70 | (no_cavity_totalpath=false) or if the particle is kept on the crest of |
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71 | RF voltage (no_cavity_totalpath=true). |
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72 | </ul> |
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73 | |
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74 | A cavity requires the particle energy |
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75 | (<a href="beam.html#energy">ENERGY</a>) |
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76 | and the particle charge |
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77 | (<a href="beam.html#charge">CHARGE</a>) |
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78 | to be set by a <a href="beam.html">BEAM</a> command |
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79 | before any calculations are performed. |
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80 | <p> |
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81 | Example: |
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82 | <pre> |
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83 | BEAM,PARTICLE=ELECTRON,ENERGY=50.0; |
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84 | CAVITY: RFCAVITY,L=10.0,VOLT=150.0,LAG=0.0,HARMON=31320; |
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85 | </pre> |
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86 | The <a href="local_system.html#straight">straight reference system</a> |
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87 | for a cavity is a cartesian coordinate system. |
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88 | <p> |
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89 | <address> |
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90 | <a href="http://www.cern.ch/Hans.Grote/hansg_sign.html">hansg</a>, |
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91 | January 24, 1997 |
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92 | </address> |
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93 | |
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94 | </body> |
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