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1 //
2 // ********************************************************************
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4 // * *
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17 // * *
18 // * This code implementation is the result of the scientific and *
19 // * technical work of the GEANT4 collaboration. *
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24 // ********************************************************************
25 //
26 // This example is provided by the Geant4-DNA collaboration
27 // Any report or published results obtained using the Geant4-DNA software
28 // shall cite the following Geant4-DNA collaboration publication:
29 // Med. Phys. 37 (2010) 4692-4708
30 // The Geant4-DNA web site is available at http://geant4-dna.org
31 //
32 // If you use this example, please cite the following publication:
33 // Rad. Prot. Dos. 133 (2009) 2-11
34 //
35 // Based on purging magnet advanced example.
36 //
37
38 #include "EMField.hh"
39 #include "G4Exp.hh"
40 #include "G4SystemOfUnits.hh"
41
42 EMField::EMField()
43 {}
44
45 void EMField::GetFieldValue(const double point[4], double *Bfield ) const
46 {
47 // Magnetic field
48 Bfield[0] = 0;
49 Bfield[1] = 0;
50 Bfield[2] = 0;
51
52 // Electric field
53 Bfield[3] = 0;
54 Bfield[4] = 0;
55 Bfield[5] = 0;
56
57 G4double Bx = 0;
58 G4double By = 0;
59 G4double Bz = 0;
60
61 G4double x = point[0];
62 G4double y = point[1];
63 G4double z = point[2];
64
65 // ***********************
66 // AIFIRA SWITCHING MAGNET
67 // ***********************
68
69 // MAGNETIC FIELD VALUE FOR 3 MeV ALPHAS
70 G4double switchingField = 0.0589768635 * tesla ;
71
72 // BEAM START
73 G4double beamStart = -10*m;
74
75 // RADIUS
76 G4double Rp = 0.698*m;
77
78 // ENTRANCE POSITION AFTER ANALYSIS MAGNET
79 G4double zS = 975*mm;
80
81 // POLE GAP
82 G4double D = 31.8*mm;
83
84 // FRINGING FIELD
85
86 G4double fieldBoundary, wc0, wc1, wc2, wc3, limitMinEntrance, limitMaxEntrance, limitMinExit, limitMaxExit;
87
88 limitMinEntrance = beamStart+zS-4*D;
89 limitMaxEntrance = beamStart+zS+4*D;
90 limitMinExit =Rp-4*D;
91 limitMaxExit =Rp+4*D;
92
93 wc0 = 0.3835;
94 wc1 = 2.388;
95 wc2 = -0.8171;
96 wc3 = 0.200;
97
98 fieldBoundary=0.62;
99
100 G4double ws, largeS, h, dhdlargeS, dhds, dlargeSds, dsdz, dsdx, zs0, Rs0, xcenter, zcenter;
101
102 // - ENTRANCE OF SWITCHING MAGNET
103
104 if ( (z >= limitMinEntrance) && (z < limitMaxEntrance) )
105 {
106 zs0 = fieldBoundary*D;
107 ws = (-z+beamStart+zS-zs0)/D;
108 dsdz = -1/D;
109 dsdx = 0;
110
111 largeS = wc0 + wc1*ws + wc2*ws*ws + wc3*ws*ws*ws;
112 h = 1./(1.+G4Exp(largeS));
113 dhdlargeS = -G4Exp(largeS)*h*h;
114 dlargeSds = wc1+ 2*wc2*ws + 3*wc3*ws*ws;
115 dhds = dhdlargeS * dlargeSds;
116
117 By = switchingField * h ;
118 Bx = y*switchingField*dhds*dsdx;
119 Bz = y*switchingField*dhds*dsdz;
120
121 }
122
123 // - HEART OF SWITCHING MAGNET
124
125 if (
126 (z >= limitMaxEntrance)
127 && (( x*x + (z -(beamStart+zS))*(z -(beamStart+zS)) < limitMinExit*limitMinExit))
128 )
129 {
130 Bx=0;
131 By = switchingField;
132 Bz=0;
133 }
134
135 // - EXIT OF SWITCHING MAGNET
136
137 if (
138 (z >= limitMaxEntrance)
139 && (( x*x + (z -(beamStart+zS))*(z -(beamStart+zS))) >= limitMinExit*limitMinExit)
140 && (( x*x + (z -(beamStart+zS))*(z -(beamStart+zS))) < limitMaxExit*limitMaxExit)
141
142 )
143 {
144
145 xcenter = 0;
146 zcenter = beamStart+zS;
147
148 Rs0 = Rp + D*fieldBoundary;
149 ws = (std::sqrt((z-zcenter)*(z-zcenter)+(x-xcenter)*(x-xcenter)) - Rs0)/D;
150
151 dsdz = (1/D)*(z-zcenter)/std::sqrt((z-zcenter)*(z-zcenter)+(x-xcenter)*(x-xcenter));
152 dsdx = (1/D)*(x-xcenter)/std::sqrt((z-zcenter)*(z-zcenter)+(x-xcenter)*(x-xcenter));
153
154 largeS = wc0 + wc1*ws + wc2*ws*ws + wc3*ws*ws*ws;
155 h = 1./(1.+G4Exp(largeS));
156 dhdlargeS = -G4Exp(largeS)*h*h;
157 dlargeSds = wc1+ 2*wc2*ws + 3*wc3*ws*ws;
158 dhds = dhdlargeS * dlargeSds;
159
160 By = switchingField * h ;
161 Bx = y*switchingField*dhds*dsdx;
162 Bz = y*switchingField*dhds*dsdz;
163
164 }
165
166 // **************************
167 // MICROBEAM LINE QUADRUPOLES
168 // **************************
169
170 // MICROBEAM LINE ANGLE
171 G4double lineAngle = -10*deg;
172
173 // X POSITION OF FIRST QUADRUPOLE
174 G4double lineX = -1295.59*mm;
175
176 // Z POSITION OF FIRST QUADRUPOLE
177 G4double lineZ = -1327*mm;
178
179 // Adjust magnetic zone absolute position
180 lineX = lineX + 5.24*micrometer*std::cos(-lineAngle); // 5.24 = 1.3 + 3.94 micrometer (cf. DetectorConstruction)
181 lineZ = lineZ + 5.24*micrometer*std::sin(-lineAngle);
182
183 // QUADRUPOLE HALF LENGTH
184 G4double quadHalfLength = 75*mm;
185
186 // QUADRUPOLE SPACING
187 G4double quadSpacing = 40*mm;
188
189 // QUADRUPOLE CENTER COORDINATES
190 G4double xoprime, zoprime;
191
192 if (z>=-1400*mm && z <-200*mm)
193 {
194 Bx=0; By=0; Bz=0;
195
196 // FRINGING FILED CONSTANTS
197 G4double c0[4], c1[4], c2[4], z1[4], z2[4], a0[4], gradient[4];
198
199 // QUADRUPOLE 1
200 c0[0] = -5.;
201 c1[0] = 2.5;
202 c2[0] = -0.1;
203 z1[0] = 60*mm;
204 z2[0] = 130*mm;
205 a0[0] = 10*mm;
206 gradient[0] = 3.406526 *tesla/m;
207
208 // QUADRUPOLE 2
209 c0[1] = -5.;
210 c1[1] = 2.5;
211 c2[1] = -0.1;
212 z1[1] = 60*mm;
213 z2[1] = 130*mm;
214 a0[1] = 10*mm;
215 gradient[1] = -8.505263 *tesla/m;
216
217 // QUADRUPOLE 3
218 c0[2] = -5.;
219 c1[2] = 2.5;
220 c2[2] = -0.1;
221 z1[2] = 60*mm;
222 z2[2] = 130*mm;
223 a0[2] = 10*mm;
224 gradient[2] = 8.505263 *tesla/m;
225
226 // QUADRUPOLE 4
227 c0[3] = -5.;
228 c1[3] = 2.5;
229 c2[3] = -0.1;
230 z1[3] = 60*mm;
231 z2[3] = 130*mm;
232 a0[3] = 10*mm;
233 gradient[3] = -3.406526*tesla/m;
234
235 // FIELD CREATED BY A QUADRUPOLE IN ITS LOCAL FRAME
236 G4double Bx_local,By_local,Bz_local;
237 Bx_local = 0; By_local = 0; Bz_local = 0;
238
239 // FIELD CREATED BY A QUADRUPOOLE IN WORLD FRAME
240 G4double Bx_quad,By_quad,Bz_quad;
241 Bx_quad = 0; By_quad=0; Bz_quad=0;
242
243 // QUADRUPOLE FRAME
244 G4double x_local,y_local,z_local;
245 x_local= 0; y_local=0; z_local=0;
246
247 G4double vars = 0;
248 G4double G0, G1, G2, G3;
249 G4double K1, K2, K3;
250 G4double P0, P1, P2, cte;
251
252 K1=0;
253 K2=0;
254 K3=0;
255 P0=0;
256 P1=0;
257 P2=0;
258 G0=0;
259 G1=0;
260 G2=0;
261 G3=0;
262 cte=0;
263
264 G4bool largeScattering=false;
265
266 for (G4int i=0;i<4; i++)
267 {
268
269 if (i==0)
270 { xoprime = lineX + quadHalfLength*std::sin(lineAngle);
271 zoprime = lineZ + quadHalfLength*std::cos(lineAngle);
272
273 x_local = (x - xoprime) * std::cos (lineAngle) - (z - zoprime) * std::sin (lineAngle);
274 y_local = y;
275 z_local = (z - zoprime) * std::cos (lineAngle) + (x - xoprime) * std::sin (lineAngle);
276 if (std::sqrt(x_local*x_local+y_local*y_local)>a0[i]) largeScattering=true;
277
278 }
279
280 if (i==1)
281 { xoprime = lineX + (3*quadHalfLength+quadSpacing)*std::sin(lineAngle);
282 zoprime = lineZ + (3*quadHalfLength+quadSpacing)*std::cos(lineAngle);
283
284 x_local = (x - xoprime) * std::cos (lineAngle) - (z - zoprime) * std::sin (lineAngle);
285 y_local = y;
286 z_local = (z - zoprime) * std::cos (lineAngle) + (x - xoprime) * std::sin (lineAngle);
287 if (std::sqrt(x_local*x_local+y_local*y_local)>a0[i]) largeScattering=true;
288 }
289
290 if (i==2)
291 { xoprime = lineX + (5*quadHalfLength+2*quadSpacing)*std::sin(lineAngle);
292 zoprime = lineZ + (5*quadHalfLength+2*quadSpacing)*std::cos(lineAngle);
293
294 x_local = (x - xoprime) * std::cos (lineAngle) - (z - zoprime) * std::sin (lineAngle);
295 y_local = y;
296 z_local = (z - zoprime) * std::cos (lineAngle) + (x - xoprime) * std::sin (lineAngle);
297 if (std::sqrt(x_local*x_local+y_local*y_local)>a0[i]) largeScattering=true;
298 }
299
300 if (i==3)
301 { xoprime = lineX + (7*quadHalfLength+3*quadSpacing)*std::sin(lineAngle);
302 zoprime = lineZ + (7*quadHalfLength+3*quadSpacing)*std::cos(lineAngle);
303
304 x_local = (x - xoprime) * std::cos (lineAngle) - (z - zoprime) * std::sin (lineAngle);
305 y_local = y;
306 z_local = (z - zoprime) * std::cos (lineAngle) + (x - xoprime) * std::sin (lineAngle);
307 if (std::sqrt(x_local*x_local+y_local*y_local)>a0[i]) largeScattering=true;
308 }
309
310
311 if ( z_local < -z2[i] )
312 {
313 G0=0;
314 G1=0;
315 G2=0;
316 G3=0;
317 }
318
319 if ( z_local > z2[i] )
320 {
321 G0=0;
322 G1=0;
323 G2=0;
324 G3=0;
325 }
326
327 if ( (z_local>=-z1[i]) & (z_local<=z1[i]) )
328 {
329 G0=gradient[i];
330 G1=0;
331 G2=0;
332 G3=0;
333 }
334
335 if ( ((z_local>=-z2[i]) & (z_local<-z1[i])) || ((z_local>z1[i]) & (z_local<=z2[i])) )
336 {
337
338 vars = ( z_local - z1[i]) / a0[i] ;
339 if (z_local<-z1[i]) vars = ( - z_local - z1[i]) / a0[i] ;
340
341
342 P0 = c0[i]+c1[i]*vars+c2[i]*vars*vars;
343
344 P1 = c1[i]/a0[i]+2*c2[i]*(z_local-z1[i])/a0[i]/a0[i];
345 if (z_local<-z1[i]) P1 = -c1[i]/a0[i]+2*c2[i]*(z_local+z1[i])/a0[i]/a0[i];
346
347 P2 = 2*c2[i]/a0[i]/a0[i];
348
349 cte = 1 + G4Exp(c0[i]);
350
351 K1 = -cte*P1*G4Exp(P0)/( (1+G4Exp(P0))*(1+G4Exp(P0)) );
352
353 K2 = -cte*G4Exp(P0)*(
354 P2/( (1+G4Exp(P0))*(1+G4Exp(P0)) )
355 +2*P1*K1/(1+G4Exp(P0))/cte
356 +P1*P1/(1+G4Exp(P0))/(1+G4Exp(P0))
357 );
358
359 K3 = -cte*G4Exp(P0)*(
360 (3*P2*P1+P1*P1*P1)/(1+G4Exp(P0))/(1+G4Exp(P0))
361 +4*K1*(P1*P1+P2)/(1+G4Exp(P0))/cte
362 +2*P1*(K1*K1/cte/cte+K2/(1+G4Exp(P0))/cte)
363 );
364
365 G0 = gradient[i]*cte/(1+G4Exp(P0));
366 G1 = gradient[i]*K1;
367 G2 = gradient[i]*K2;
368 G3 = gradient[i]*K3;
369
370 }
371
372 // PROTECTION AGAINST LARGE SCATTERING
373
374 if ( largeScattering )
375 {
376 G0=0;
377 G1=0;
378 G2=0;
379 G3=0;
380 }
381
382 // MAGNETIC FIELD COMPUTATION FOR EACH QUADRUPOLE
383
384 Bx_local = y_local*(G0-(1./12)*(3*x_local*x_local+y_local*y_local)*G2);
385 By_local = x_local*(G0-(1./12)*(3*y_local*y_local+x_local*x_local)*G2);
386 Bz_local = x_local*y_local*(G1-(1./12)*(x_local*x_local+y_local*y_local)*G3);
387
388 Bx_quad = Bz_local*std::sin(lineAngle)+Bx_local*std::cos(lineAngle);
389 By_quad = By_local;
390 Bz_quad = Bz_local*std::cos(lineAngle)-Bx_local*std::sin(lineAngle);
391
392 // TOTAL MAGNETIC FIELD
393
394 Bx = Bx + Bx_quad ;
395 By = By + By_quad ;
396 Bz = Bz + Bz_quad ;
397
398 } // LOOP ON QUADRUPOLES
399
400
401 } // END OF QUADRUPLET
402
403 Bfield[0] = Bx;
404 Bfield[1] = By;
405 Bfield[2] = Bz;
406
407 // *****************************************
408 // ELECTRIC FIELD CREATED BY SCANNING PLATES
409 // *****************************************
410
411 Bfield[3] = 0;
412 Bfield[4] = 0;
413 Bfield[5] = 0;
414
415 // POSITION OF EXIT OF LAST QUAD WHERE THE SCANNING PLATES START
416
417 G4double electricPlateWidth1 = 5 * mm;
418 G4double electricPlateWidth2 = 5 * mm;
419 G4double electricPlateLength1 = 36 * mm;
420 G4double electricPlateLength2 = 34 * mm;
421 G4double electricPlateGap = 5 * mm;
422 G4double electricPlateSpacing1 = 3 * mm;
423 G4double electricPlateSpacing2 = 4 * mm;
424
425 // APPLY VOLTAGE HERE IN VOLTS (no electrostatic deflection here)
426 G4double electricPlateVoltage1 = 0 * volt;
427 G4double electricPlateVoltage2 = 0 * volt;
428
429 G4double electricFieldPlate1 = electricPlateVoltage1 / electricPlateSpacing1 ;
430 G4double electricFieldPlate2 = electricPlateVoltage2 / electricPlateSpacing2 ;
431
432 G4double beginFirstZoneX = lineX + (8*quadHalfLength+3*quadSpacing)*std::sin(lineAngle);
433 G4double beginFirstZoneZ = lineZ + (8*quadHalfLength+3*quadSpacing)*std::cos(lineAngle);
434
435 G4double beginSecondZoneX = lineX + (8*quadHalfLength+3*quadSpacing+electricPlateLength1+electricPlateGap)*std::sin(lineAngle);
436 G4double beginSecondZoneZ = lineZ + (8*quadHalfLength+3*quadSpacing+electricPlateLength1+electricPlateGap)*std::cos(lineAngle);
437
438 G4double xA, zA, xB, zB, xC, zC, xD, zD;
439 G4double slope1, cte1, slope2, cte2, slope3, cte3, slope4, cte4;
440
441 // WARNING : lineAngle < 0
442
443 // FIRST PLATES
444
445 xA = beginFirstZoneX + std::cos(lineAngle)*electricPlateSpacing1/2;
446 zA = beginFirstZoneZ - std::sin(lineAngle)*electricPlateSpacing1/2;
447
448 xB = xA + std::sin(lineAngle)*electricPlateLength1;
449 zB = zA + std::cos(lineAngle)*electricPlateLength1;
450
451 xC = xB - std::cos(lineAngle)*electricPlateSpacing1;
452 zC = zB + std::sin(lineAngle)*electricPlateSpacing1;
453
454 xD = xC - std::sin(lineAngle)*electricPlateLength1;
455 zD = zC - std::cos(lineAngle)*electricPlateLength1;
456
457 slope1 = (xB-xA)/(zB-zA);
458 cte1 = xA - slope1 * zA;
459
460 slope2 = (xC-xB)/(zC-zB);
461 cte2 = xB - slope2 * zB;
462
463 slope3 = (xD-xC)/(zD-zC);
464 cte3 = xC - slope3 * zC;
465
466 slope4 = (xA-xD)/(zA-zD);
467 cte4 = xD - slope4 * zD;
468
469
470 if
471 (
472 x <= slope1 * z + cte1
473 && x >= slope3 * z + cte3
474 && x <= slope4 * z + cte4
475 && x >= slope2 * z + cte2
476 && std::abs(y)<=electricPlateWidth1/2
477 )
478
479 {
480 Bfield[3] = electricFieldPlate1*std::cos(lineAngle);
481 Bfield[4] = 0;
482 Bfield[5] = -electricFieldPlate1*std::sin(lineAngle);
483
484 }
485
486 // SECOND PLATES
487
488 xA = beginSecondZoneX + std::cos(lineAngle)*electricPlateWidth2/2;
489 zA = beginSecondZoneZ - std::sin(lineAngle)*electricPlateWidth2/2;
490
491 xB = xA + std::sin(lineAngle)*electricPlateLength2;
492 zB = zA + std::cos(lineAngle)*electricPlateLength2;
493
494 xC = xB - std::cos(lineAngle)*electricPlateWidth2;
495 zC = zB + std::sin(lineAngle)*electricPlateWidth2;
496
497 xD = xC - std::sin(lineAngle)*electricPlateLength2;
498 zD = zC - std::cos(lineAngle)*electricPlateLength2;
499
500 slope1 = (xB-xA)/(zB-zA);
501 cte1 = xA - slope1 * zA;
502
503 slope2 = (xC-xB)/(zC-zB);
504 cte2 = xB - slope2 * zB;
505
506 slope3 = (xD-xC)/(zD-zC);
507 cte3 = xC - slope3 * zC;
508
509 slope4 = (xA-xD)/(zA-zD);
510 cte4 = xD - slope4 * zD;
511
512 if
513 (
514 x <= slope1 * z + cte1
515 && x >= slope3 * z + cte3
516 && x <= slope4 * z + cte4
517 && x >= slope2 * z + cte2
518 && std::abs(y)<=electricPlateSpacing2/2
519 )
520
521 {
522 Bfield[3] = 0;
523 Bfield[4] = electricFieldPlate2;
524 Bfield[5] = 0;
525 }
526
527 }
528