US 2009/0117314 Al  16  May  7,  2009  [0219]  The mean values found were -40.7 kV/m (rounded  up to -41 kV/m) for F  mean’  -58.3 kV/m for F  min  and -22.6  kV/m for F  max•  The difference between the mean maximum  and mean minimum electric field strength F  max  and F  min’  which is referred to as field strength variation in the context of  the invention, is thus -22.6-(-58.3)=35.7 kV/m (rounded up  to 36 kV/m).  TABLE 3-continued  TABLE 4-continued  (Individual results for electrostatic  field measurements for Exam12le 2)  Individual disc  Fmean  Fm;n  Fmax  nwnber  (kV/m)  (kV/m)  (kV/m)  89  -43.9  -59.8  -27.6  90  -39.6  -55.8  -23.9  91  -43.4  -63.0  -23.3  92  -40.6  -57.2  -19.6  93  -41.9  -61.8  -22.8  94  -42.8  -58.8  -25.4  95  -46.1  -63.5  -27.2  96  -43.9  -61.4  -22.4  97  -48.8  -61.6  -32.4  98  -42.8  -61.3  -22.6  99  -27.1  -36.7  -19.0  100  -45.4  -65.8  -20.6  Mean value  -40.7  -58.3  -22.6  forall 100  discs  (Individual results for electrostatic  field measurement for Exam12le 21)  Individual disc  Fmean  Fm;n  Fmax  nwnber  (kV/m)  (kV/m)  (kV/m)  -0.3  -5.1  2.9  2  0.1  -3.2  2.9  3  0.3  -4.0  3.7  4  1.5  -3.5  4.6  5  -2.0  -5.1  0.7  6  0.3  -3.8  4.8  7  0.5  -4.0  5.2  8  0.4  -2.9  4.2  9  0.6  -5.3  3.6  10  1.0  -4.3  3.7  11  -1.2  -5.6  2.2  12  0.0  -4.6  2.5  13  0.9  -4.1  3.8  14  0.6  -5.3  3.2  15  0.2  -4.9  2.9  16  -0.7  -4.2  2.2  17  0.6  -3.9  3.9  18  -0.1  -3.7  2.3  19  -2.5  -8.3  2.0  20  0.4  -5.1  4.4  21  -0.1  -4.9  3.8  22  0.8  -3.8  3.4  23  0.9  -3.4  3.1  24  0.8  -4.3  3.4  25  0.7  -6.4  4.9  26  -0.9  -4.9  2.3  27  1.2  -4.8  4.0  28  0.1  -5.0  4.8  29  -0.7  -4.8  1.7  30  0.2  -3.5  2.3  31  1.3  -4.2  4.0  32  0.3  -10.0  5.9  33  -0.5  -3.8  3.0  34  0.4  -4.4  3.0  35  -0.9  -7.2  2.4  (Individual results for electrostatic  field measurement for Exam12le 21)  Individual disc  Fmean  Fm;n  Fmax  nwnber  (kV/m)  (kV/m)  (kV/m)  36  0.3  -5.3  3.2  37  0.2  -3.6  2.7  38  -2.0  -6.4  2.4  39  0.0  -4.8  3.4  40  0.9  -3.0  3.1  41  0.9  -3.6  3.5  42  0.5  -4.1  4.4  43  0.6  -4.6  3.6  44  -1.6  -8.1  2.8  45  -0.2  -4.3  4.7  46  -0.8  -5.6  2.4  47  0.7  -4.8  3.3  48  0.7  -3.7  3.3  49  -0.8  -4.6  2.0  50  0.1  -4.3  2.7  51  -1.2  -4.7  2.5  52  -0.2  -7.0  3.5  53  0.4  -2.5  2.8  54  0.5  -3.2  3.2  55  1.1  -2.7  3.7  56  -1.6  -10.0  2.2  57  1.1  -2.7  3.4  58  1.7  -3.4  4.4  59  1.6  -4.3  4.4  60  1.2  -3.7  4.5  61  1.1  -4.5  4.1  62  1.2  -10.7  5.1  63  -0.7  -6.0  2.2  64  1.1  -3.1  3.3  65  1.7  -0.3  3.4  66  0.7  -8.3  4.3  67  1.4  -3.6  4.1  68  -1.1  -10.0  2.6  69  0.6  -4.0  3.1  70  0.5  -3.5  3.6  71  0.5  -4.5  3.8  72  -1.0  -4.8  2.6  73  -1.0  -4.4  1.6  74  0.4  -4.0  5.4  75  0.9  -3.6  4.3  76  -0.8  -5.2  2.7  77  -1.1  -7.4  2.0  78  -0.3  -6.0  2.7  79  -0.5  -4.7  2.8  80  1.5  -3.8  4.1  81  1.1  -3.2  4.0  82  0.6  -4.0  2.8  83  -0.2  -6.6  4.1  84  1.3  -3.1  3.5  85  1.2  -3.4  3.5  86  -0.7  -9.1  2.4  87  1.3  -3.4  4.1  88  1.2  -3.9  4.4  89  1.2  -7.5  4.5  90  0.8  -3.9  3.3  91  1.7  -3.6  4.4  92  0.0  -4.2  3.7  93  0.8  -4.2  4.1  94  0.7  -3.8  3.9  95  1.1  -3.9  3.9  96  0.0  -2.4  2.6  97  -1.5  -6.2  2.0  98  0.7  -4.1  4.4  99  1.0  -3.8  4.3  100  1.2  -4.1  4.4  Mean value  0.3  -4.7  3.4  forall 100  discs  TABLE4 