source: trunk/examples/advanced/microbeam/src/MicrobeamEMField.cc@ 1179

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19// * technical work of the GEANT4 collaboration. *
20// * By using, copying, modifying or distributing the software (or *
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24// ********************************************************************
25//
26// -------------------------------------------------------------------
27// $Id: MicrobeamEMField.cc,v 1.6 2007/07/06 06:52:54 sincerti Exp $
28// -------------------------------------------------------------------
29
30#include "MicrobeamEMField.hh"
31
32MicrobeamEMField::MicrobeamEMField()
33{
34}
35
36void MicrobeamEMField::GetFieldValue(const double point[4], double *Bfield ) const
37{
38 // Magnetic field
39 Bfield[0] = 0;
40 Bfield[1] = 0;
41 Bfield[2] = 0;
42
43 // Electric field
44 Bfield[3] = 0;
45 Bfield[4] = 0;
46 Bfield[5] = 0;
47
48 G4double Bx = 0;
49 G4double By = 0;
50 G4double Bz = 0;
51
52 G4double x = point[0];
53 G4double y = point[1];
54 G4double z = point[2];
55
56// ***********************
57// AIFIRA SWITCHING MAGNET
58// ***********************
59
60 // MAGNETIC FIELD VALUE FOR 3 MeV ALPHAS
61 G4double switchingField = 0.0589768635 * tesla ;
62
63 // BEAM START
64 G4double beamStart = -10*m;
65
66 // RADIUS
67 G4double Rp = 0.698*m;
68
69 // ENTRANCE POSITION AFTER ANALYSIS MAGNET
70 G4double zS = 975*mm;
71
72 // POLE GAP
73 G4double D = 31.8*mm;
74
75 // FRINGING FIELD
76
77 G4double fieldBoundary, wc0, wc1, wc2, wc3, limitMinEntrance, limitMaxEntrance, limitMinExit, limitMaxExit;
78
79 limitMinEntrance = beamStart+zS-4*D;
80 limitMaxEntrance = beamStart+zS+4*D;
81 limitMinExit =Rp-4*D;
82 limitMaxExit =Rp+4*D;
83
84 wc0 = 0.3835;
85 wc1 = 2.388;
86 wc2 = -0.8171;
87 wc3 = 0.200;
88
89 fieldBoundary=0.62;
90
91 G4double ws, largeS, h, dhdlargeS, dhds, dlargeSds, dsdz, dsdx, zs0, Rs0, xcenter, zcenter;
92
93// - ENTRANCE OF SWITCHING MAGNET
94
95if ( (z >= limitMinEntrance) && (z < limitMaxEntrance) )
96{
97 zs0 = fieldBoundary*D;
98 ws = (-z+beamStart+zS-zs0)/D;
99 dsdz = -1/D;
100 dsdx = 0;
101
102 largeS = wc0 + wc1*ws + wc2*ws*ws + wc3*ws*ws*ws;
103 h = 1./(1.+std::exp(largeS));
104 dhdlargeS = -std::exp(largeS)*h*h;
105 dlargeSds = wc1+ 2*wc2*ws + 3*wc3*ws*ws;
106 dhds = dhdlargeS * dlargeSds;
107
108 By = switchingField * h ;
109 Bx = y*switchingField*dhds*dsdx;
110 Bz = y*switchingField*dhds*dsdz;
111
112}
113
114// - HEART OF SWITCHING MAGNET
115
116 if (
117 (z >= limitMaxEntrance)
118 && (( x*x + (z -(beamStart+zS))*(z -(beamStart+zS)) < limitMinExit*limitMinExit))
119 )
120{
121 Bx=0;
122 By = switchingField;
123 Bz=0;
124}
125
126// - EXIT OF SWITCHING MAGNET
127
128if (
129 (z >= limitMaxEntrance)
130 && (( x*x + (z -(beamStart+zS))*(z -(beamStart+zS))) >= limitMinExit*limitMinExit)
131 && (( x*x + (z -(beamStart+zS))*(z -(beamStart+zS))) < limitMaxExit*limitMaxExit)
132
133 )
134{
135
136 xcenter = 0;
137 zcenter = beamStart+zS;
138
139 Rs0 = Rp + D*fieldBoundary;
140 ws = (std::sqrt((z-zcenter)*(z-zcenter)+(x-xcenter)*(x-xcenter)) - Rs0)/D;
141
142 dsdz = (1/D)*(z-zcenter)/std::sqrt((z-zcenter)*(z-zcenter)+(x-xcenter)*(x-xcenter));
143 dsdx = (1/D)*(x-xcenter)/std::sqrt((z-zcenter)*(z-zcenter)+(x-xcenter)*(x-xcenter));
144
145 largeS = wc0 + wc1*ws + wc2*ws*ws + wc3*ws*ws*ws;
146 h = 1./(1.+std::exp(largeS));
147 dhdlargeS = -std::exp(largeS)*h*h;
148 dlargeSds = wc1+ 2*wc2*ws + 3*wc3*ws*ws;
149 dhds = dhdlargeS * dlargeSds;
150
151 By = switchingField * h ;
152 Bx = y*switchingField*dhds*dsdx;
153 Bz = y*switchingField*dhds*dsdz;
154
155}
156
157// **************************
158// MICROBEAM LINE QUADRUPOLES
159// **************************
160
161 // MICROBEAM LINE ANGLE
162 G4double lineAngle = -10*deg;
163
164 // X POSITION OF FIRST QUADRUPOLE
165 G4double lineX = -1295.59*mm;
166
167 // Z POSITION OF FIRST QUADRUPOLE
168 G4double lineZ = -1327*mm;
169
170 // Adjust magnetic zone absolute position
171 lineX = lineX + 5.24*micrometer*std::cos(-lineAngle); // 5.24 = 1.3 + 3.94 micrometer (cf. DetectorConstruction)
172 lineZ = lineZ + 5.24*micrometer*std::sin(-lineAngle);
173
174 // QUADRUPOLE HALF LENGTH
175 G4double quadHalfLength = 75*mm;
176
177 // QUADRUPOLE SPACING
178 G4double quadSpacing = 40*mm;
179
180 // QUADRUPOLE CENTER COORDINATES
181 G4double xoprime, zoprime;
182
183if (z>=-1400*mm & z <-200*mm)
184{
185 Bx=0; By=0; Bz=0;
186
187 // FRINGING FILED CONSTANTS
188 G4double c0[4], c1[4], c2[4], z1[4], z2[4], a0[4], gradient[4];
189
190 // QUADRUPOLE 1
191 c0[0] = -5.;
192 c1[0] = 2.5;
193 c2[0] = -0.1;
194 z1[0] = 60*mm;
195 z2[0] = 130*mm;
196 a0[0] = 10*mm;
197 gradient[0] = 3.406526 *tesla/m;
198
199 // QUADRUPOLE 2
200 c0[1] = -5.;
201 c1[1] = 2.5;
202 c2[1] = -0.1;
203 z1[1] = 60*mm;
204 z2[1] = 130*mm;
205 a0[1] = 10*mm;
206 gradient[1] = -8.505263 *tesla/m;
207
208 // QUADRUPOLE 3
209 c0[2] = -5.;
210 c1[2] = 2.5;
211 c2[2] = -0.1;
212 z1[2] = 60*mm;
213 z2[2] = 130*mm;
214 a0[2] = 10*mm;
215 gradient[2] = 8.505263 *tesla/m;
216
217 // QUADRUPOLE 4
218 c0[3] = -5.;
219 c1[3] = 2.5;
220 c2[3] = -0.1;
221 z1[3] = 60*mm;
222 z2[3] = 130*mm;
223 a0[3] = 10*mm;
224 gradient[3] = -3.406526*tesla/m;
225
226 // FIELD CREATED BY A QUADRUPOLE IN ITS LOCAL FRAME
227 G4double Bx_local,By_local,Bz_local;
228 Bx_local = 0; By_local = 0; Bz_local = 0;
229
230 // FIELD CREATED BY A QUADRUPOOLE IN WORLD FRAME
231 G4double Bx_quad,By_quad,Bz_quad;
232 Bx_quad = 0; By_quad=0; Bz_quad=0;
233
234 // QUADRUPOLE FRAME
235 G4double x_local,y_local,z_local;
236 x_local= 0; y_local=0; z_local=0;
237
238 G4double s = 0;
239 G4double G0, G1, G2, G3;
240 G4double K0, K1, K2, K3;
241 G4double P0, P1, P2, P3, cte;
242
243 K0=0;
244 K1=0;
245 K2=0;
246 K3=0;
247 P0=0;
248 P1=0;
249 P2=0;
250 P3=0;
251 G0=0;
252 G1=0;
253 G2=0;
254 G3=0;
255 cte=0;
256
257 G4bool largeScattering=false;
258
259 for (G4int i=0;i<4; i++)
260 {
261
262 if (i==0)
263 { xoprime = lineX + quadHalfLength*std::sin(lineAngle);
264 zoprime = lineZ + quadHalfLength*std::cos(lineAngle);
265
266 x_local = (x - xoprime) * std::cos (lineAngle) - (z - zoprime) * std::sin (lineAngle);
267 y_local = y;
268 z_local = (z - zoprime) * std::cos (lineAngle) + (x - xoprime) * std::sin (lineAngle);
269 if (std::sqrt(x_local*x_local+y_local*y_local)>a0[i]) largeScattering=true;
270
271 }
272
273 if (i==1)
274 { xoprime = lineX + (3*quadHalfLength+quadSpacing)*std::sin(lineAngle);
275 zoprime = lineZ + (3*quadHalfLength+quadSpacing)*std::cos(lineAngle);
276
277 x_local = (x - xoprime) * std::cos (lineAngle) - (z - zoprime) * std::sin (lineAngle);
278 y_local = y;
279 z_local = (z - zoprime) * std::cos (lineAngle) + (x - xoprime) * std::sin (lineAngle);
280 if (std::sqrt(x_local*x_local+y_local*y_local)>a0[i]) largeScattering=true;
281 }
282
283 if (i==2)
284 { xoprime = lineX + (5*quadHalfLength+2*quadSpacing)*std::sin(lineAngle);
285 zoprime = lineZ + (5*quadHalfLength+2*quadSpacing)*std::cos(lineAngle);
286
287 x_local = (x - xoprime) * std::cos (lineAngle) - (z - zoprime) * std::sin (lineAngle);
288 y_local = y;
289 z_local = (z - zoprime) * std::cos (lineAngle) + (x - xoprime) * std::sin (lineAngle);
290 if (std::sqrt(x_local*x_local+y_local*y_local)>a0[i]) largeScattering=true;
291 }
292
293 if (i==3)
294 { xoprime = lineX + (7*quadHalfLength+3*quadSpacing)*std::sin(lineAngle);
295 zoprime = lineZ + (7*quadHalfLength+3*quadSpacing)*std::cos(lineAngle);
296
297 x_local = (x - xoprime) * std::cos (lineAngle) - (z - zoprime) * std::sin (lineAngle);
298 y_local = y;
299 z_local = (z - zoprime) * std::cos (lineAngle) + (x - xoprime) * std::sin (lineAngle);
300 if (std::sqrt(x_local*x_local+y_local*y_local)>a0[i]) largeScattering=true;
301 }
302
303
304 if ( z_local < -z2[i] )
305 {
306 G0=0;
307 G1=0;
308 G2=0;
309 G3=0;
310 }
311
312 if ( z_local > z2[i] )
313 {
314 G0=0;
315 G1=0;
316 G2=0;
317 G3=0;
318 }
319
320 if ( (z_local>=-z1[i]) & (z_local<=z1[i]) )
321 {
322 G0=gradient[i];
323 G1=0;
324 G2=0;
325 G3=0;
326 }
327
328 if ( ((z_local>=-z2[i]) & (z_local<-z1[i])) || ((z_local>z1[i]) & (z_local<=z2[i])) )
329 {
330
331 s = ( z_local - z1[i]) / a0[i] ;
332 if (z_local<-z1[i]) s = ( - z_local - z1[i]) / a0[i] ;
333
334
335 P0 = c0[i]+c1[i]*s+c2[i]*s*s;
336
337 P1 = c1[i]/a0[i]+2*c2[i]*(z_local-z1[i])/a0[i]/a0[i];
338 if (z_local<-z1[i]) P1 = -c1[i]/a0[i]+2*c2[i]*(z_local+z1[i])/a0[i]/a0[i];
339
340 P2 = 2*c2[i]/a0[i]/a0[i];
341
342 P3 = 0;
343
344 cte = 1 + std::exp(c0[i]);
345
346 K1 = -cte*P1*std::exp(P0)/( (1+std::exp(P0))*(1+std::exp(P0)) );
347
348 K2 = -cte*std::exp(P0)*(
349 P2/( (1+std::exp(P0))*(1+std::exp(P0)) )
350 +2*P1*K1/(1+std::exp(P0))/cte
351 +P1*P1/(1+std::exp(P0))/(1+std::exp(P0))
352 );
353
354 K3 = -cte*std::exp(P0)*(
355 (3*P2*P1+P1*P1*P1)/(1+std::exp(P0))/(1+std::exp(P0))
356 +4*K1*(P1*P1+P2)/(1+std::exp(P0))/cte
357 +2*P1*(K1*K1/cte/cte+K2/(1+std::exp(P0))/cte)
358 );
359
360 G0 = gradient[i]*cte/(1+std::exp(P0));
361 G1 = gradient[i]*K1;
362 G2 = gradient[i]*K2;
363 G3 = gradient[i]*K3;
364
365 }
366
367 // PROTECTION AGAINST LARGE SCATTERING
368
369 if ( largeScattering )
370 {
371 G0=0;
372 G1=0;
373 G2=0;
374 G3=0;
375 }
376
377 // MAGNETIC FIELD COMPUTATION FOR EACH QUADRUPOLE
378
379 Bx_local = y_local*(G0-(1./12)*(3*x_local*x_local+y_local*y_local)*G2);
380 By_local = x_local*(G0-(1./12)*(3*y_local*y_local+x_local*x_local)*G2);
381 Bz_local = x_local*y_local*(G1-(1./12)*(x_local*x_local+y_local*y_local)*G3);
382
383 Bx_quad = Bz_local*std::sin(lineAngle)+Bx_local*std::cos(lineAngle);
384 By_quad = By_local;
385 Bz_quad = Bz_local*std::cos(lineAngle)-Bx_local*std::sin(lineAngle);
386
387 // TOTAL MAGNETIC FIELD
388
389 Bx = Bx + Bx_quad ;
390 By = By + By_quad ;
391 Bz = Bz + Bz_quad ;
392
393 } // LOOP ON QUADRUPOLES
394
395
396} // END OF QUADRUPLET
397
398 Bfield[0] = Bx;
399 Bfield[1] = By;
400 Bfield[2] = Bz;
401
402// *****************************************
403// ELECTRIC FIELD CREATED BY SCANNING PLATES
404// *****************************************
405
406 Bfield[3] = 0;
407 Bfield[4] = 0;
408 Bfield[5] = 0;
409
410 // POSITION OF EXIT OF LAST QUAD WHERE THE SCANNING PLATES START
411
412 G4double electricPlateWidth1 = 5 * mm;
413 G4double electricPlateWidth2 = 5 * mm;
414 G4double electricPlateLength1 = 36 * mm;
415 G4double electricPlateLength2 = 34 * mm;
416 G4double electricPlateGap = 5 * mm;
417 G4double electricPlateSpacing1 = 3 * mm;
418 G4double electricPlateSpacing2 = 4 * mm;
419
420 // APPLY VOLTAGE HERE IN VOLTS (no electrostatic deflection here)
421 G4double electricPlateVoltage1 = 0 * volt;
422 G4double electricPlateVoltage2 = 0 * volt;
423
424 G4double electricFieldPlate1 = electricPlateVoltage1 / electricPlateSpacing1 ;
425 G4double electricFieldPlate2 = electricPlateVoltage2 / electricPlateSpacing2 ;
426
427 G4double beginFirstZoneX = lineX + (8*quadHalfLength+3*quadSpacing)*std::sin(lineAngle);
428 G4double beginFirstZoneZ = lineZ + (8*quadHalfLength+3*quadSpacing)*std::cos(lineAngle);
429
430 G4double beginSecondZoneX = lineX + (8*quadHalfLength+3*quadSpacing+electricPlateLength1+electricPlateGap)*std::sin(lineAngle);
431 G4double beginSecondZoneZ = lineZ + (8*quadHalfLength+3*quadSpacing+electricPlateLength1+electricPlateGap)*std::cos(lineAngle);
432
433 G4double xA, zA, xB, zB, xC, zC, xD, zD;
434 G4double slope1, cte1, slope2, cte2, slope3, cte3, slope4, cte4;
435
436 // WARNING : lineAngle < 0
437
438 // FIRST PLATES
439
440 xA = beginFirstZoneX + std::cos(lineAngle)*electricPlateSpacing1/2;
441 zA = beginFirstZoneZ - std::sin(lineAngle)*electricPlateSpacing1/2;
442
443 xB = xA + std::sin(lineAngle)*electricPlateLength1;
444 zB = zA + std::cos(lineAngle)*electricPlateLength1;
445
446 xC = xB - std::cos(lineAngle)*electricPlateSpacing1;
447 zC = zB + std::sin(lineAngle)*electricPlateSpacing1;
448
449 xD = xC - std::sin(lineAngle)*electricPlateLength1;
450 zD = zC - std::cos(lineAngle)*electricPlateLength1;
451
452 slope1 = (xB-xA)/(zB-zA);
453 cte1 = xA - slope1 * zA;
454
455 slope2 = (xC-xB)/(zC-zB);
456 cte2 = xB - slope2 * zB;
457
458 slope3 = (xD-xC)/(zD-zC);
459 cte3 = xC - slope3 * zC;
460
461 slope4 = (xA-xD)/(zA-zD);
462 cte4 = xD - slope4 * zD;
463
464
465 if
466 (
467 x <= slope1 * z + cte1
468 && x >= slope3 * z + cte3
469 && x <= slope4 * z + cte4
470 && x >= slope2 * z + cte2
471 && std::abs(y)<=electricPlateWidth1/2
472 )
473
474 {
475 Bfield[3] = electricFieldPlate1*std::cos(lineAngle);
476 Bfield[4] = 0;
477 Bfield[5] = -electricFieldPlate1*std::sin(lineAngle);
478
479 }
480
481 // SECOND PLATES
482
483 xA = beginSecondZoneX + std::cos(lineAngle)*electricPlateWidth2/2;
484 zA = beginSecondZoneZ - std::sin(lineAngle)*electricPlateWidth2/2;
485
486 xB = xA + std::sin(lineAngle)*electricPlateLength2;
487 zB = zA + std::cos(lineAngle)*electricPlateLength2;
488
489 xC = xB - std::cos(lineAngle)*electricPlateWidth2;
490 zC = zB + std::sin(lineAngle)*electricPlateWidth2;
491
492 xD = xC - std::sin(lineAngle)*electricPlateLength2;
493 zD = zC - std::cos(lineAngle)*electricPlateLength2;
494
495 slope1 = (xB-xA)/(zB-zA);
496 cte1 = xA - slope1 * zA;
497
498 slope2 = (xC-xB)/(zC-zB);
499 cte2 = xB - slope2 * zB;
500
501 slope3 = (xD-xC)/(zD-zC);
502 cte3 = xC - slope3 * zC;
503
504 slope4 = (xA-xD)/(zA-zD);
505 cte4 = xD - slope4 * zD;
506
507 if
508 (
509 x <= slope1 * z + cte1
510 && x >= slope3 * z + cte3
511 && x <= slope4 * z + cte4
512 && x >= slope2 * z + cte2
513 && std::abs(y)<=electricPlateSpacing2/2
514 )
515
516 {
517 Bfield[3] = 0;
518 Bfield[4] = electricFieldPlate2;
519 Bfield[5] = 0;
520 }
521
522// ZERO FIELD REGIONS
523
524if (
525(Bfield[0]==0. &
526Bfield[1]==0. &
527Bfield[2]==0. &
528Bfield[4]==0. &
529Bfield[5]==0. &
530Bfield[6]==0. )
531)
532{
533
534G4FieldManager *pFieldMgr;
535pFieldMgr = G4TransportationManager::GetTransportationManager()->GetFieldManager();
536pFieldMgr = NULL;
537
538}
539
540//
541
542
543}
544
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