1. The rate is higher when the HV is higher. The rate is higher when the threshold is lower. The rate is higher when the target density is high.
2. Too large raster size lead to high background
3. The rates is high, when the beam is not stable
4. Background scale with the current on the same target
5. At 5 pass, by comparing the empty reference cell and the 3He, we conclude 80% of the background is from reference cell.
6. Background with sieve in is smaller than the one with sieve out.
7 The shielding we added and the new collimator (not the one for the beam pipe window) give a 15% effect.
8. On 3He reference cell, the background rates reduce 30% when we go from 1 pass beam to 2 pass beam. The background rates reduce another 45% when we go from 2 pass beam to 5 pass beam. The total improvement is more than 60% from 1 pass to 5 pass. (This include the 15% improvement for adding new shileding and collimator).
9. At first pass the rates between C1:C2:C3 is 1.34:1.44:1.0. At second pass, the rates between C1:C2:C3 is 1.1:1.17:1. At 5 pass, the rates between C1:C2:C3 is 0.98:1:23:1.
10. With magnet off, the rates on first chamber is about 100MHz, however the dark current is still ok.
11 At five pass, we have C1:C2:C3 = 3.8 MHz: 4.5 MHz : 4.3 MHz per 1 uA for the first cell. The number for the second cell is 3.5 : 4.5 : 4.2 MHz per 1uA. The rate reduce a little bit, since the pressure may be lower for the second cell.
We will need to take a look at the effect of the new collimator.
*****************************************************************************
Details
Single Carbon
Second pass Single carbon foils
runnumber, average current, beam energy, BG1, BG2, BG3
neglect the last two colums, and BG1 means the background for chamber 1 averaged by the current.
2846 4.67093 2.396 9.07705 8.98951 5.06022 0.307913 0.00976667
2845 4.95954 2.396 9.0039 8.91744 5.03631 0.312922 0.00990673
2844 5.08608 2.396 8.99915 8.93464 5.00908 0.365734 0.0127971
Multi-Carbon
The rate is quite similar for multi carbon foils run, no matter that is the current
3618 0.189525 5.889 13.9597 14.9138 11.9391 0.06458 0.00125333
2970 4.00758 5.889 12.5164 13.1163 10.3946 0.225802 0.0170668
2968 1.82162 5.889 14.6876 15.1601 11.3286 0.17869 0.00699746
2964 4.88924 5.889 12.1036 12.7378 10.2521 0.246867 0.0225933
2962 2.86983 5.889 13.5171 14.0942 10.9364 0.0574684 0.00175447
2961 3.01676 5.889 13.4611 14.0407 10.9076 0.0589471 0.00185335
2960 2.57832 5.889 13.4908 14.0576 10.8973 0.0511141 0.00159296
2958 2.90622 5.889 13.5348 14.0858 10.9569 0.0585775 0.00185201
2957 2.78242 5.889 13.5596 14.131 10.9588 0.0564937 0.00178668
2956 3.00221 5.889 13.4767 14.0683 10.9327 0.060318 0.00209442
2954 3.14097 5.889 13.5017 14.0457 10.6305 0.180482 0.00764256
2951 5.299 5.889 11.7728 12.2601 10.0398 0.241593 0.0233067
2947 3.58248 5.889 12.4172 12.9059 10.3477 0.216497 0.0151698
2946 3.07062 5.889 12.3233 12.7849 10.3564 0.213195 0.0125622
2945 2.94226 5.889 12.2306 12.7256 10.2864 0.210188 0.0111418
2944 1.92255 5.889 13.0215 13.4524 10.6482 0.191016 0.00834138
2943 2.22537 5.889 12.8363 13.2953 10.6254 0.0406736 0.000980007
two pass beam rate is similar to five pass
2886 1.96522 2.396 13.0495 13.1289 10.1344 0.342033 0.00833333
2885 1.99197 2.396 13.003 13.0946 10.0144 0.344767 0.00854667
sieve out in first pass, the background is higher than 2nd and 5 pass.
2659 1.94411 1.23 20.489 21.9047 15.2142 0.621937 0.0111867
2658 1.93284 1.23 19.3895 20.6775 14.3032 0.626444 0.00948006
2657 1.94821 1.23 19.4812 20.7358 14.3162 0.492541 0.00840213
2650 0.848011 1.23 19.9542 20.9911 14.5512 0.00606 2.66667e-05
This run is magnet off. lots of low energy stuff, but not large dark current is fine. (Interesting)
2641 0.921394 1.23 117.177 116.958 18.3003 0.591873 0.0900667
sieve in The background level is smaller than sieve out run
2585 4.31146 1.23 13.8508 14.6175 7.48015 0.459563 0.0137201
2582 4.39544 1.23 13.9492 14.7142 7.51946 0.461113 0.0150333
reference cell H2
4014 11.2568 5.889 3.46187 4.34246 3.65098 0.1909 0.00975333
4013 11.5656 5.889 3.46019 4.34517 3.64553 0.19404 0.01004
4012 11.3866 5.889 3.46016 4.34748 3.64713 0.191867 0.00972667
3942 11.3847 5.889 3.2796 4.12238 3.35871 0.191755 0.00946673
3941 11.394 5.889 3.28403 4.12752 3.35887 0.191867 0.00906
3940 11.787 5.889 3.27488 4.11238 3.35655 0.194073 0.00954
These runs are due to beam tuning
3286 2.07093 5.889 5.43633 6.03216 4.76275 0.00704667 6e-05
3285 2.05185 5.889 5.45389 6.05477 4.78058 0.00658667 3.33333e-05
3284 1.7647 5.889 5.54211 6.21772 4.97923 0.00575333 2e-05
3283 1.96107 5.889 5.39789 5.95359 4.68159 0.00588135 2.85502e-05
second pass sieve out, rate is higher than 5 pass
2904 3.84276 2.396 5.1373 5.29868 3.87372 0.349704 0.00422823
2903 4.19423 2.396 5.09348 5.27208 3.85028 0.379347 0.00471333
2902 3.45685 2.396 5.11872 5.30457 3.84334 0.0680536 0.000493653
2897 3.92018 2.396 5.16858 5.34033 3.89882 0.347107 0.00444
2896 3.8155 2.396 5.17255 5.3535 3.89401 0.344553 0.00416
2893 4.05718 2.396 5.14688 5.32725 3.89671 0.3489 0.00417333
2892 3.7534 2.396 5.18307 5.36327 3.91999 0.340373 0.00382667
sieve in, rate is lower than the sieve out run
2869 4.94867 2.396 4.03241 4.03225 2.17442 0.34586 0.00304667
2868 4.96316 2.396 3.92173 3.90732 2.14529 0.338487 0.0028
2866 4.72024 2.396 4.03556 4.0295 2.16925 0.3355 0.00236
2865 4.86636 2.396 4.03456 4.03245 2.15682 0.337853 0.00250667
2864 4.72289 2.396 4.05494 4.05329 2.19683 0.22746 0.00189333
2852 1.93914 2.396 4.91344 4.83092 2.52551 0.360967 0.00289333
2851 2.01945 2.396 4.91049 4.83286 2.52667 0.363253 0.00276
2850 1.98518 2.396 4.92125 4.82522 2.51028 0.359407 0.0028
2847 7.3492 2.396 4.63892 4.63796 2.49262 0.188801 0.00296002
These are the threshold and HV scan, rates are higher when the HV is higher or the threshold is lower
1650 + 3.5 V
2685 1.72291 1.23 12.2057 13.3082 9.50286 0.480219 0.00400117
1650 + 4.0V
2684 2.0892 1.23 11.4936 12.5096 8.84428 0.495099 0.00413549
1650 + 4.5V
2683 2.04255 1.23 11.1484 12.1435 8.5713 0.500836 0.00415233
1650 + 5.0V
2682 1.81637 1.23 11.0712 12.0718 8.44012 0.507425 0.00333214
1550 + 5.0V
2681 1.82323 1.23 8.86306 9.42724 6.60712 0.483394 0.0017937
1550 + 4.5V
2680 1.97943 1.23 9.0395 9.70446 6.85989 0.51719 0.00264319
1550 + 4.0V
2679 1.75381 1.23 9.42102 10.1693 7.13414 0.542088 0.00271599
1550 + 3.5V
2678 1.75899 1.23 9.67786 10.4546 7.34888 0.54923 0.00329754
1550 + 3.0V
2677 1.79008 1.23 9.9638 10.7769 7.58926 0.542637 0.00326192
1500 + 3.0V
2676 2.30766 1.23 8.48994 9.09366 6.51045 0.44623 0.00248046
1500 + 4.0V
2674 2.29701 1.23 7.65378 8.02825 5.77458 0.210723 0.00064744
1500 + 4.5V
2673 2.21942 1.23 7.24323 7.5164 5.38512 0.118234 0.000270072
1500 + 5.0V
2672 2.06816 1.23 6.86352 7.07275 5.02221 0.057475 6.69203e-05
1600 + 5.0V
2671 1.78938 1.23 10.0348 10.8669 7.67328 0.542029 0.00334943
1600 + 4.5V
2670 1.97533 1.23 10.1546 10.9842 7.77619 0.541571 0.00399294
1600 + 4.0V
2669 1.89475 1.23 10.4294 11.2939 8.01602 0.533764 0.00410295
1600 + 3.0V 2668 1.9056 1.23 11.0937 12.0601 8.56418 0.512073 0.00401645
1600 + 3.5V sieve out 2666 1.85109 1.23 10.7801 11.7277 8.29799 0.522674 0.0041606
2664 1.93926 1.23 10.5676 11.499 8.11036 0.5265 0.00366667
2660 1.87621 1.23 10.4002 11.3256 7.91279 0.463586 0.00343694
2663 2.03858 1.23 10.4459 11.3048 8.00073 0.52568 0.00362667
2662 1.99827 1.23 10.5103 11.3971 8.03963 0.527653 0.00385333
sieve in run in first pass, the rate is lower than sieve out run
2633 1.78828 1.23 7.82255 7.95385 4.18372 0.46388 0.00145333
2632 0.90210 1.23 8.11132 8.26986 4.19264 0.463633 0.00109333
2629 0.99101 1.23 8.40817 8.63248 4.46425 0.463493 0.00113333
2624 0.28064 1.23 8.28214 8.70947 4.47389 0.0413149 0.000142301
2604 5.01666 1.23 8.50572 8.95142 4.53239 0.263297 0.00256372
beam tuning
2620 0.96540 1.23 9.35927 9.52543 5.3044 0.115473 0.000526667
2614 0.94302 1.23 10.7585 10.8503 5.6252 0.57156 0.00178
2613 0.99403 1.23 11.044 11.105 5.76637 0.575413 0.00211333
2612 1.04271 1.23 10.8427 10.92 5.68454 0.57802 0.0019
2611 1.01808 1.23 10.9225 10.9927 5.6719 0.578347 0.00208
2610 0.98875 1.23 11.366 11.4142 6.03939 0.579447 0.00218
N2data
pressure 20psig
4010 11.6932 5.889 4.0198 5.04793 4.45353 0.220955 0.0164734
4009 11.2016 5.889 4.04732 5.09582 4.48859 0.215167 0.0155733
4008 9.67266 5.889 4.11216 5.18183 4.55485 0.207271 0.0140085
3939 11.6724 5.889 4.15517 5.23129 4.64779 0.222408 0.0182801
3934 11.3273 5.889 4.16782 5.2588 4.664 0.2193 0.0175867
3931 11.2677 5.889 4.16432 5.21655 4.64402 0.216659 0.0174006
pressure 100psig
3282 1.96958 5.889 10.473 11.693 10.8406 0.0262333 0.000406667
3281 2.26364 5.889 10.3199 11.4844 10.5732 0.0305933 0.00052
3279 2.18303 5.889 9.71474 10.6823 9.54764 0.0277916 0.00034266
pressre 50psig
2918 1.99368 2.396 8.11019 8.47274 6.8722 0.360018 0.0058254
2917 1.98579 2.396 8.06489 8.46214 6.82837 0.0148484 0.000179137
2916 2.04135 2.396 8.0489 8.44301 6.82444 0.0154467 0.000126667
2915 1.88838 2.396 8.14762 8.56423 6.92097 0.381732 0.00616915
2914 2.09692 2.396 7.9709 8.45287 6.72433 0.0140575 0
2913 2.04483 2.396 8.1729 8.5239 6.66991 0.0172702 0
2907 1.91982 2.396 8.16135 8.54129 6.88152 0.36134 0.00532667
1st pass trig!! pressure scan
2559 5.29056 1.23 7.60471 7.4369 4.14489 0.0177333 0.00143333
N2 pressure ~ 246 torr
2524 4.69149 1.23 9.89994 10.4611 6.43899 0.0212735 0.000353336
N2 pressure ~ 510 torr
2523 4.35171 1.23 10.2622 10.8647 6.7714 0.0689538 0.000813339
765 torr
2522 4.66098 1.23 11.4481 12.1992 7.94162 0.0825006 0.00167334
950 torr
2521 4.68852 1.23 12.3153 13.1583 8.7502 0.131701 0.00385336
950 torr
2520 4.71689 1.23 12.3971 13.1556 8.7613 0.0948951 0.00282426
950 torr
2519 4.34867 1.23 12.8662 13.6869 9.11378 0.0802706 0.00210276
515 torr.
2517 4.72041 1.23 9.80474 10.3065 6.59345 0.0747272 0.00102001
507 torr.
2516 4.74451 1.23 9.53598 9.99812 6.35487 0.0688805 0.000873339
266 torr
2515 4.41825 1.23 9.46317 9.91849 6.27052 0.06824 0.00078
ure 3 torr.
2514 4.55156 1.23 9.21638 9.62683 5.9756 0.0618537 0.00054667
re 749 torr
2513 4.61167 1.23 10.2039 10.7289 6.96307 0.0773472 0.00112001
reference 3He data 3 energy runs from first pass to 5 pass, improve more than a factor of 2.
2564 4.61776 1.23 10.0454 10.8125 7.48501 0.114647 0.00432
2563 4.88235 1.23 10.9602 11.6051 7.14126 0.09366 0.00408667
4005 10.8809 5.889 3.38005 4.23468 3.48439 0.192887 0.0104067
3949 11.3533 5.889 3.31355 4.161 3.38478 0.189388 0.00950006
3946 11.8713 5.889 3.30076 4.13643 3.37455 0.196387 0.01006
3945 11.5341 5.889 3.30051 4.14206 3.37517 0.194193 0.00984
2922 1.97366 2.396 7.11114 7.57777 6.48057 0.31718 0.00384667
2921 1.99182 2.396 7.10596 7.54307 6.4787 0.318627 0.00374
2920 1.81167 2.396 7.14193 7.58229 6.49638 0.29748 0.00372
2919 1.9698 2.396 7.15823 7.56401 6.48512 0.311813 0.00342
empty reference raster size change
3x4 raster size
4007 11.4213 5.889 2.76085 3.44538 2.51669 0.2132 0.0077526
4006 10.5255 5.889 2.776 3.47252 2.51562 0.18469 0.00621703
3929 4.89064 5.889 2.74376 3.40178 2.44653 0.186893 0.00352667
3923 5.01379 5.889 2.93821 3.79588 2.6847 0.194133 0.00390667
different beam position? slightly higher than above
3541 1.86719 5.889 3.28279 3.75036 2.96604 0.232715 0.00299335
3540 1.80735 5.889 3.21022 3.70337 2.91882 0.258592 0.00278288
3539 1.8739 5.889 3.22734 3.72941 2.95936 0.264549 0.00266255
3538 1.9824 5.889 3.17856 3.6735 2.83333 0.296809 0.0037938
N2 in the cell
3930 5.03349 5.889 3.7956 4.73739 4.03699 0.177433 0.00626624
5*6.5 raster
3927 1.89417 5.889 3.2603 4.21602 2.90328 0.00497952 0
3926 1.95549 5.889 3.16921 4.15467 2.75569 0.0058361 6.68256e-05
3925 1.96553 5.889 3.13285 4.07754 2.7371 0.00556575 2.03874e-05
beam trip!!
3542 1.82395 5.889 1.28077 1.28932 1.02121 0.0721667 0.000893333
5x6
3275 2.03877 5.889 5.40557 5.60552 3.50721 0.00624078 0.00020574
4x5
3273 1.98153 5.889 4.176 4.4487 3.01578 0.00455057 0
2.5x3
3271 1.66312 5.889 3.89525 4.11759 2.71481 0.00380458 1.67602e-05
3270 1.965 5.889 3.85245 4.09403 2.8398 0.00456533 3.86892e-05
3x4
3268 2.03831 5.889 6.3187 6.94812 6.02927 0.013661 0.00082926
2.5x3
3267 2.19367 5.889 2.00874 2.14353 1.39417 0.00244494 0
empty
beam tune 2509 2.90436 1.23 16.4406 17.5463 12.5161 0.0217135 0.000260002
2505 2.82326 1.23 17.859 19.0421 13.5373 0.0246203 0.000449236
2x2
2325 5.08008 1.23 4.2994 4.53177 2.56811 0.0265267 0
2324 4.91173 1.23 4.30762 4.53365 2.5644 0.0248138 6.72097e-06
2323 4.87545 1.23 4.35167 4.5812 2.59184 0.02644 0
2322 5.08998 1.23 4.35943 4.58319 2.60349 0.0248 6.66667e-06
2321 4.89342 1.23 4.36836 4.60076 2.62061 0.0247884 6.84763e-06
2320 4.94491 1.23 4.36208 4.60392 2.62289 0.0262827 7.3109e-06
2319 5.16267 1.23 4.33874 4.5735 2.61053 0.02582 0
2318 5.25545 1.23 4.33154 4.57546 2.61615 0.0262562 0
2317 5.19533 1.23 4.37278 4.60763 2.62919 0.05514 0
2316 4.97971 1.23 4.39772 4.62156 2.64202 0.0537333 0
2315 4.77045 1.23 4.41954 4.63722 2.6462 0.05356 2e-05
real polarized 3He, the average rates is quite similar
RUN 3556 is with new collimator and shielding. Compared with RUN 3021, the rates reduce by a bout 15%.
3021 7.97504 5.9 4.68492 5.23143 4.5515 0.256623 0.0116291
3556 8.28536 5.9 3.77395 4.4809 4.29501 0.204275 0.00916673
3569 11.3584 5.9 3.65593 4.35755 4.02504 0.20616 0.01124
3571 11.2944 5.9 3.65142 4.35109 4.0919 0.207993 0.0113867
RUN 3541, 3542, 3543 is the empty referene cell, and 3544 is the 3He The background rates is about 80% of the 3He rates
3541 1.86719 5.9 3.28279 3.75036 2.96604 0.232715 0.00299335
3543 1.94121 5.9 3.18378 3.66135 2.88962 0.239073 0.00302
3544 1.95769 5.9 3.97802 4.71563 4.52142 0.165533 0.00343333
Background is very similar, by scanning the current
3018 1.98209 5.9 5.03532 5.55658 4.83986 0.230573 0.0037012
3019 3.69325 5.9 4.88407 5.40834 4.71405 0.234663 0.00590446
3020 5.78568 5.9 4.76234 5.30384 4.62295 0.243494 0.00865559
3021 7.97504 5.9 4.68492 5.23143 4.5515 0.256623 0.0116291
3022 9.73255 5.9 4.63156 5.16448 4.52227 0.266201 0.0146022
3023 9.71271 5.9 4.66147 5.22138 4.5366 0.262625 0.0154721
different HV settings
1600V
3032 2.15946 5.9 5.04022 5.58662 4.84224 0.237825 0.00449471
1650V
3033 1.94897 5.9 5.84464 6.42662 5.44551 0.236422 0.00452348
1700V
3034 1.95179 5.9 7.03842 7.47304 6.28947 0.234326 0.00497759
1700V
3035 1.19218 5.9 7.37401 7.81979 6.57345 0.230152 0.00353357
1650V
3036 1.19131 5.9 6.03348 6.56762 5.62791 0.232815 0.00355174
1600V
3037 0.95790 5.9 5.32927 5.80697 5.04749 0.227772 0.00305459
1550V
3038 0.930574 5.9 4.60269 5.02584 4.38054 0.15725 0.00163984
new polarized 3He cell
4079 8 11.5111 3.53784 4.5189 4.21531 0.194212 0.0127401
A copy of this log entry has been emailed to: jpchen@jlab.org,jiang@jlab.org