source: specdomain/trunk/src/specdomain/macros/usaxs_uascan.mac @ 985

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1#
2#  usaxs_uascan.mac
3#
4#  USAXS-specific macros
5#  maintained by Jan Ilavsky
6#  last edit:  2012-02-29
7# 
8########### SVN repository information ###################
9# $Date: 2012-04-02 13:51:57 -0500 (Mon, 02 Apr 2012) $
10# $Author: jemian $
11# $Revision: 524 $
12# $HeadURL: https://subversion.xor.aps.anl.gov/spec/beamline_config/trunk/usaxs/usaxs/usaxs_uascan.mac $
13# $Id: usaxs_uascan.mac 524 2012-04-02 18:51:57Z jemian $
14########### SVN repository information ###################
15#
16# this file contains the USAXSscan,  uascan macro (1-D & 2-D collimated USAXS) and supporting subprograms.
17# June 02 - replaced all lax:upd2 with brq:pd01:seq01 to move UPD to e-brick
18# Oct. 6 - X Jiao Oct.6
19# 2007-09-10,PRJ: replaced all "lax:" with "15iddLAX:"
20# September 27, 2007 replaced all "brq:" with "32idbUSX:" since the PVV names changed. JIL
21# OCT 2008 JIL - changed to epics variables
22# NOV 3 2008 changed Finish to be in Q units, JIL
23# MAY 09, chaned ar controls to new DC driven Aeortech stage, JIL
24# JUNE 10, changed all 32idbLAX/USXto 15iddLAX/USX after moved to 15idd
25# OCOTOBER 10, JIL - Changed to be able to use Femto300 amlifier
26# APRIL 20, 2011, PAB - Added useDynamicTime settings.
27# APRIL 26, 2011, PAB - Added useIntelligentTime setting.
28# February 29, 2012, JIL - added delay in uascan after PD range change to fix some problems.
29#  globals:
30# these numbers should be mostly set in USAXS_conf.mac or other configuration file...
31
32global     useSBUSAXS                    # set to 1 if running SBUSAXS geometry, else 0
33global     SAMPLE_DETECTOR_DISTANCE_MM   # need to set configuration in USAXS.conf
34global     SAMPLE_ANALYZER_DISTANCE_MM   # need to set configuration in USAXS.conf
35global     ARenc_CENTER                  # AR center in encoder value... Probably not needed anymore
36global     SPEC_STD_TITLE                # scan title
37global     USAXS_SAMPLE_THICKNESS        # sample thickness
38global     ASRP_DEGREES_PER_VDC          # calibration constant for asrp
39global     Use_DLPCA300                            # if 1, using Femto300 amplifier, if 0 usign Femto200
40global     PDstring
41global     useDynamicTime                # if 1, use dynamic count time (change count time 3 times during a scan at fixed point numbers).  if 0, use static.
42global     useIntelligentTime            # if 1, use intelligent count time (nondeterministic method, chooses count time based on upd range).  if 0, use static. 
43global     old_UPDRange                  # UPDRange for the last point
44global     UPD_Change_delay              # delay in usaxs scan after range change
45
46global     CT_RANGE_1
47global     CT_RANGE_2
48global     CT_RANGE_3
49global     CT_RANGE_4
50global     CT_RANGE_5
51
52# these are now epics variables
53#global     ASRP0                            # start value of Asrp
54#global     USAXS_TIME                    # time to measure each point in USAX sscan
55#global     AR_VAL_CENTER                 # center value for AR stage
56#global     NUMPTS                        # number of points
57#global     DY0                              # start position of detector stage
58#global     SDD                           # sample to detector disatnce
59#global     AY0                           # start analyzer height
60#global     SAD                           # sample to analyzer distacne
61#global     UATERM                        # weighing value... Changes spread of the log stepping
62#global     SAMPLE_Y_STEP                 # sample Y movement, mm, to make after each step in the scan
63#global     START_OFFSET                  # angle offset to start above AR_VAL_CENTER
64#global     FINISH                        # end angle for USAXS scans
65#global     USAXS_MINSTEP                 # min step of uascan   
66
67#
68#
69#  ASRP calibration. 8/2/2006 Found two different numbers...
70#   ASRP_DEGREES_PER_VDC = 0.0039065  # (4.5 um/V) / (66mm arm) * (180/pi)
71##  ASRP_DEGREES_PER_VDC = 0.00586     # reported by PI, note sais, that it is confirmed by measurement
72  ASRP_DEGREES_PER_VDC = 0.0059721     # measured by JI October 9, 2006 during setup at 32ID. Std Dev 4e-5
73#######
74#############################################################################
75#############################################################################
76#############################################################################
77###################################################################################
78###################################################################################
79####
80####  general scan macro for USAXS for both 1D & 2D collimations
81####
82def USAXSscan '{
83  local pos_X pos_Y scan_title Finish_in_Angle _USAXS_Lambda
84
85  global ARenc_CENTER
86  global SPEC_STD_TITLE
87  global USAXS_SAMPLE_THICKNESS
88  global useSBUSAXS
89  global USAXS_MEASURE_DARK_CURENTS
90  if( $# != 4) {
91    printf ("USAXSscan pos_X pos_Y thickness_mm scan_title\n");
92    exit;
93  }
94  pos_X = $1
95  pos_Y = $2
96  USAXS_SAMPLE_THICKNESS = $3
97  scan_title = \'$4\'
98
99  # need to check pos_X and pos_Y against soft limits before proceeding
100  _bad_lim = 0
101  _chk_lim sx pos_X
102  _chk_lim sy pos_Y
103  if (_bad_lim) {
104    printf("sample position (%.3f,%.3f) exceeds soft limits\n", pos_X, pos_Y)
105    exit;
106  }
107
108  SPEC_STD_TITLE = TITLE
109  TITLE      = scan_title
110
111  epics_put ("15iddLAX:USAXS:sampleTitle", scan_title)
112  epics_put ("15iddLAX:USAXS:state",       sprintf("USAXS count time: %g seconds", USAXS_TIME))
113  epics_put ("15iddLAX:USAXS:userName",    USER)
114  epics_put ("15iddLAX:USAXS:userDir",     CWD)
115  epics_put ("15iddLAX:USAXS:specFile",    DATAFILE)
116  epics_put ("15iddLAX:USAXS:specScan",    SCAN_N+1)
117  if (useSBUSAXS) {
118    epics_put ("15iddLAX:USAXS:scanMacro",   "sbuascan")
119  } else {
120    epics_put ("15iddLAX:USAXS:scanMacro",   "uascan")
121  }
122  epics_put ("15iddLAX:USAXS:timeStamp",   date())
123
124  comment "Moving AR motor to %g degrees (beam center)" AR_VAL_CENTER
125  mv ar AR_VAL_CENTER
126  waitmove; get_angles;
127  sleep (0.5)
128  ARenc_CENTER = A[ar]
129  comment "for next scan: encoder ARenc_CENTER  = %7.4f" ARenc_CENTER
130
131     # Set the center for the Q calculation for plotting here
132  epics_put("15iddLAX:USAXS:Q.B", ARenc_CENTER-0.00005)
133
134  START      = AR_VAL_CENTER + START_OFFSET
135  MINSTEP    = USAXS_MINSTEP    # JI 10 26 2006 change to allow user specified min step
136  TIME       = USAXS_TIME
137
138  epics_put ("15iddLAX:USAXS:state",       "moving sample into beam")
139  moveSample pos_X pos_Y
140 
141  #Calculate Finish in angle, since now it is in Q units
142  #use en as energy in keV,
143  _USAXS_Lambda = 12.4 / A[en]
144  Finish_in_Angle = AR_VAL_CENTER - (360/PI)*asin( FINISH * _USAXS_Lambda / (4*PI))
145
146  # cleanup macro for ^C usage
147  rdef _cleanup3 \'resetUSAXS\'
148
149  epics_put ("15iddLAX:USAXS:state",       "starting USAXS scan")
150 
151  comment "uascan started"
152 
153  uascan ar START AR_VAL_CENTER Finish_in_Angle MINSTEP DY0 SDD AY0 SAD UATERM NUMPNTS TIME
154
155  comment "uascan finished"
156 
157 
158  if (USAXS_MEASURE_DARK_CURENTS) {
159      epics_put ("15iddLAX:USAXS:state",       "measuring dark currents")
160      measure_USAXS_PD_dark_currents
161  }
162 
163  comment "Moving AR motor back to %g degrees (beam center)" AR_VAL_CENTER
164  mv ar AR_VAL_CENTER
165  waitmove; get_angles
166
167  # normal cleanup macro for ^C usage
168  rdef _cleanup3 \'\'
169  comment %s scan_title
170  TITLE = SPEC_STD_TITLE
171  epics_put ("15iddLAX:USAXS:state",       "scan finished")
172}'
173####################################################
174##### resetUSAXS macro
175####################################################
176
177def resetUSAXS '{
178  global SPEC_STD_TITLE
179  global useSBUSAXS
180  global NOTIFY_ON_RESET
181  comment "Resetting USAXS"
182  epics_put ("15iddLAX:USAXS:state",       "resetting motors")
183  setplot 131
184  closeTiFilterShutter
185           # speed the motor up for the return
186     # epics_put("15iddLAX:xps:c0:m2.S", "2.0")
187     # clear the user bit to indicate USAXS scan is not running
188  epics_put ("15iddLAX:USAXS:scanning",  0)
189     waitmove; get_angles
190     A[dy] = DY0
191     A[ay] = AY0
192     A[ar] = AR_VAL_CENTER
193     if(useSBUSAXS){
194       A[asrp] = ASRP0
195     }
196     move_em; waitmove
197  TITLE = SPEC_STD_TITLE
198  epics_put (sprintf("15iddUSX:%s:mode",PDstring), 2)
199  epics_put (sprintf("%s.CONT",_SCALER_PV), 1) #from jfk:vsc:c0 -xjiao
200         # set a moderate motor speed for general use
201        #  epics_put("15iddLAX:xps:c0:m2.S", "1.0")
202  epics_put ("15iddLAX:USAXS:state",       "USAXS reset complete")
203  if(NOTIFY_ON_RESET) { sendNotifications("USAXS has reset","spec has encountered a problem and reset the USAXS.");}
204  chk_beam_off
205  rdef _cleanup3 \'\'
206}'
207
208#############################################################################
209#############################################################################
210#############################################################################
211#
212#  uascan scans the one motor (AR assumed).
213#  (uascan stands for USAXS ascan, incorporating a step
214#  size that varies with distance from a center point.)
215#########################################################################
216#
217# `uascan' is a single-motor scan with adjustable step size
218#
219def uascan '
220  if ($# != 12) {
221    printf("Usage: uascan %s %s %s\n",         \
222       "motor start center finish minStep",    \
223       "dy0 SDD_mm ay0 SAD_mm",                \
224       "exponent intervals time")
225    exit
226  }
227  local _s
228  local _f
229  local _d 
230  local _center
231  local _asrp0
232 
233         # read header into internal (local) parameters.
234         # Do they have to be declared local or global or just left as is?
235  _s = $2; _center = $3; _f = $4; _ms = $5
236  _dy0    = $6;
237  SAMPLE_DETECTOR_DISTANCE_MM = $7;
238  _ay0    = $8;
239  SAMPLE_ANALYZER_DISTANCE_MM = $9;
240  _exp    = $10
241  _n1     = int($11)
242  _ctime  = $12
243  _ctime_base = _ctime
244 
245  if(useDynamicTime)
246  {
247        _ctime = _ctime_base / 3
248  }
249  if(useIntelligentTime)
250  {     
251        _ctime = CT_RANGE_1
252  }
253        # end of reading the header
254 
255        # declare variables to store current values...
256        local old_dy              # position of photodiode before scan
257        local old_ay              # position of AY before scan
258        local old_sy              # position of SY before scan
259        local old_ar              # position of AR motor before scan
260      local old_ASRP            # position of ASRP motor before scan
261
262        # check some basic conditions   
263      if (_n1 <= 0) {
264                print "Intervals <= 0"
265                exit
266        }
267         _bad_lim = 0
268         _chk_lim ar _s
269         _chk_lim ar _f
270         if (_bad_lim) exit;
271
272        # set heading for scans to show if we are running USAXS or SBUSAXS
273        HEADING = (useSBUSAXS) ?  "sbuascan " : "uascan "
274        HEADING=sprintf("%s%s",HEADING,sprintf(" %s %g %g %g %g ",\
275                "ar",_s,_center,_f,_ms))
276        HEADING=sprintf("%s %g %g",HEADING,_dy0,SAMPLE_DETECTOR_DISTANCE_MM)
277        HEADING=sprintf("%s %g %g",HEADING,_ay0,SAMPLE_ANALYZER_DISTANCE_MM)
278        HEADING=sprintf("%s %g %g %g",HEADING,_exp,_n1,_ctime)
279
280
281         # find appropriate factor for weighing the points
282        _d = uascanFindFactor(_s, _center, _f, _n1, _exp, _ms)
283        _dir = (_s < _f) ? 1 : -1
284        _n1++   
285        _cols=1
286        X_L = motor_name(ar)
287        Y_L = cnt_name(DET)
288        _sx = _s; _fx = _f
289        _stype = 1
290        FPRNT=PPRNT=VPRNT=""
291        FPRNT=sprintf("%s%s  ",FPRNT,motor_name(ar))
292        PPRNT=sprintf("%s%8.8s ",PPRNT,motor_name(ar))
293        VPRNT=sprintf("%s%9.9s ",VPRNT,motor_name(ar))
294        scan_head
295        PFMT=sprintf("%%s%%8.%df ",UP)
296        VFMT=sprintf("%%s%%9.%df ",UP)
297        # UP is user precision, defined in standard.mac as 4
298        # it can be redefined to show more decimal places if needed
299
300        # count the actual number of data points in this scan
301        def _scan_on \'
302          local scan_over
303          scan_over = 0
304             # _s is next point calculate during last point, or start angle from call to macro
305          _pos = _s   
306         for (; NPTS < _n1; NPTS++) {
307                local  target_sy   target_ay   target_dy
308                 ### set Ar angle to target
309                A[ar] = _pos
310
311                     ### re-position DY on the scattered beam
312                target_dy = _dy0 + _usaxs_triangulate (A[ar], AR_VAL_CENTER, SAMPLE_DETECTOR_DISTANCE_MM)
313                A[dy] = target_dy
314
315                     ### re-position AY on the scattered beam
316                target_ay = _ay0 + _usaxs_triangulate (A[ar], AR_VAL_CENTER, SAMPLE_ANALYZER_DISTANCE_MM)
317                A[ay] = target_ay
318
319                target_sy = A[sy]
320                if (NPTS > 0) {
321                     ### (maybe) re-position the sample before each step after the first
322                  target_sy = A[sy] + SAMPLE_Y_STEP
323                  A[sy] = target_sy
324                }
325                   ### ASRP stuff, more complicated...   
326            if(useSBUSAXS){
327                   ### adjust the ASRP piezo on the AS side-bounce stage
328                     tanBragg = tan(_center*PI/180)
329                     cosScatAngle = cos((_center-A[ar])*PI/180)
330                    diff = atan(tanBragg/cosScatAngle)*180/PI - _center
331                    # on 11 19 2003 the original (Pete) formula with sin replaced
332                    # by Jan and Andrew with formulas using tan... Should be correct...
333                    # this is original Petes formula .... diff = asin(sinBragg/cosScatAngle)*180/PI - _center
334                        #
335                        # Note on asrp adjustment:  NOTE: seems wrong, but may need to be revisited???
336                        #   use "-" when reflecting  inboard towards storage ring (single bounce setup)
337                        #   use "+" when reflecting outboard towards experimenters (channel-cut setup)
338                        ### on 2/06/2002 Andrew realized, that we are moving in wrong direction
339                    ## the sign change to - moves ASRP towards larger Bragg angles...
340                    ## verified experimentally - higher voltage on piezo = lower Bragg angle...
341                        ## and we need to INCREASE the Bragg Angle with increasing Q, to correct for tilt down...
342                        #######p "updating the piezo with" asrp_vdc
343                        ###old-style###epics_put (asrp_control_PV, asrp_vdc)
344                 asrp_vdc = _asrp0 - diff/ASRP_DEGREES_PER_VDC
345                     A[asrp] = asrp_vdc
346                 #######p "ASRP has been updated"
347            }
348
349                ### write comment for GUI
350                epics_put ("15iddLAX:USAXS:state", sprintf("%s %d/%d", "moving motors", NPTS+1, _n1-1))
351                   ### move to point
352                scan_move
353                   ### spec stuff
354                FPRNT=PPRNT=VPRNT=""
355              FPRNT=sprintf("%s%.8g ",FPRNT,A[ar])
356              PPRNT=sprintf(PFMT,PPRNT,A[ar])
357              VPRNT=sprintf(VFMT,VPRNT,A[ar])
358                   ### write comment for GUI
359            epics_put ("15iddLAX:USAXS:state", sprintf("%s %d/%d", "counting", NPTS+1, _n1-1))
360               ### spec stuff...
361
362               ## wait if range changed
363         if(fabs(old_UPDRange-UPDRange)>0){
364               #print "Sleeping due to range change"
365               sleep (UPD_Change_delay)
366           }   
367         old_UPDRange = UPDRange             
368                scan_loop
369                scan_data(NPTS,A[ar])
370                scan_plot
371                       ### calculate position for next step here
372            _pos += _dir * uascanStepFunc(_pos, _d, _center, _exp, _ms)
373                   
374            if(useDynamicTime){
375                if(NPTS < (_n1/3)) { _ctime = _ctime_base / 2 }
376                if(NPTS > (_n1/3) && NPTS < ((2/3)*_n1)) { _ctime = _ctime_base }
377                if(NPTS > ((2/3)*_n1)) { _ctime = 2*_ctime_base}
378            }
379
380          if(useIntelligentTime) {
381                updRange = epics_get("15iddUSX:pd01:seq02:reqrange","short")
382                if(updRange==0)
383                {
384                        _ctime = CT_RANGE_1
385                }
386                else if(updRange == 1)
387                {
388                        _ctime = CT_RANGE_2
389                }
390                else if(updRange == 2)
391                {
392                        _ctime = CT_RANGE_3
393                }
394                else if(updRange == 3)
395                {
396                        _ctime = CT_RANGE_4
397                }
398                else
399                {
400                        _ctime = CT_RANGE_5
401                }
402          }
403           
404                       ### check if done.
405             if (_dir > 0) {
406                    if (_pos > _f) scan_over = 1
407                  } else {
408                    if (_pos < _f) scan_over = 1
409                  }
410                if (scan_over == 1) break
411         }
412         scan_tail
413        \'
414           ### remember pre-scan motor positions: AY, SY, DY, and AR
415        old_ay    = A[ay]
416        old_sy    = A[sy]
417        old_dy    = A[dy]
418        old_ar    = A[ar]
419      if(useSBUSAXS){
420         old_ASRP   = A[asrp]
421         _asrp0     = A[asrp]
422      }
423           # make the scaler wait before counting
424        epics_put(sprintf("%s.DLY",_SCALER_PV), MOTOR_PRESCALER_WAIT)
425           # turn off the AutoCount mode on the scaler
426        epics_put(sprintf("%s.CONT",_SCALER_PV), "0")
427           # turn on the photodiode automatic range changer, automatic mode
428        epics_put(sprintf("15iddUSX:%s:mode",PDstring), "1")
429           # slow the AR motor down for the scan
430                 #  epics_put("15iddLAX:xps:c0:m2.S", 0.5) old motor
431         #  When using the USAXS_chk_beam macro,
432         #  test for the "beam dumped" condition by
433         #  setting a threshold on the I0 monitor counts.
434         #  Specify here using a minimum I0 count rate.
435      chk_thresh = _ctime * 2000
436           # close the shutter just in case it is important
437      closeTiFilterShutter
438           # rotate AR (or MR) to the starting position
439      epics_put ("15iddLAX:USAXS:state",       "rotate to first angle")
440      waitmove; get_angles
441      A[ar] = _s
442      move_em; waitmove
443           # open the shutters just before each scan to preserve the detector
444      openTiFilterShutter
445      openMonoShutter
446         # set the photodiode on mid-range
447      epics_put(sprintf("15iddUSX:%s:reqrange.VAL",PDstring), 2);
448         # set a bit to indicate USAXS scan is running
449      if (useSBUSAXS) {
450          epics_put ("15iddLAX:USAXS:scanMacro", "sbuascan")
451      } else {
452          epics_put ("15iddLAX:USAXS:scanMacro", "uascan")
453      }
454      epics_put ("15iddLAX:USAXS:scanning", 1)
455     
456        ###------------------------
457      # def chk_beam \'USAXS_chk_beam\'
458      #setplot 163          ;#  163 turns on log(Yaxis)
459      #setplot 131          ;#  131 turns off log(Yaxis)
460      setplot 131             ;#  0 turns off plot during scan
461
462        _scan_on
463
464      # def chk_beam \'standard_chk_beam\'
465        ###------------------------
466         # clear the user bit to indicate USAXS scan is not running
467      epics_put ("15iddLAX:USAXS:scanning.VAL",  0)
468           # close the shutter after each scan to preserve the detector
469        closeTiFilterShutter
470           # turn on the AutoCount mode on the scaler
471        epics_put(sprintf("%s.CONT",_SCALER_PV), "1") #from jfk
472           # turn on the photodiode automatic range changer, auto+bkg mode
473        epics_put(sprintf("15iddUSX:%s:mode",PDstring), "2")
474           # speed the motor up for the return
475                # epics_put("15iddLAX:xps:c0:m2.S", "2.0") old motor
476           # reset motors to pre-scan positions: AY, SY, DY, and "the first motor" (AR)
477      epics_put ("15iddLAX:USAXS:state",       "returning AR, AY, SY, and DY")
478            get_angles
479            A[ay]    = old_ay
480            A[sy]    = old_sy
481            A[dy]    = old_dy
482            A[ar]    = old_ar
483          if(useSBUSAXS){
484              A[asrp]  = old_ASRP
485          } 
486            move_em; waitmove
487         # set a moderate motor speed for general use
488                # epics_put("15iddLAX:xps:c0:m2.S", "0.5") old motor
489'
490
491#############################################################################
492#############################################################################
493#############################################################################
494#############################################################################
495#############################################################################
496#############################################################################
497#
498#    subprograms....
499#
500# uascanStepFunc
501#
502# Calculate the next step size with the given parameters
503#
504uascanStepDebug = 0
505def uascanStepFunc(x, factor, center, exponent, minStep) '{
506  local step
507  step = factor * pow( fabs(x - center), exponent ) + minStep
508  if (uascanStepDebug >= 2)
509    printf ("step = %g\n", step)
510  return step
511}'
512
513# uascanTestSeries
514#
515# Make a series with the specified parameters
516#  If factor is too large, return the number of points required to reach finish.
517#  Otherwise, return the closeness of the final point to the finish.
518#
519def uascanTestSeries(start, center, finish, numPts, factor, exponent, minStep) '{
520  local x step i dir
521
522  x = start
523  dir = (start < finish) ? 1 : -1
524  for (i=1; i < numPts; i++) {
525    step = uascanStepFunc(x, factor, center, exponent, minStep)
526    x += dir*step
527    if ( ((dir>0) && (x > finish))  ||  ((dir<0) && (x < finish)) ) {
528      return i
529    }
530  }
531  return (-1 * fabs(x - finish))
532}'
533
534# uascanFindFactor
535#
536# Determine the factor that will make a series with the specified parameters.
537#  Choose the factor that will minimize | x[n] - finish |  subject to:
538#    x[1] = start
539#    x[n] <= finish
540# This routine CAN FAIL if (finish - start)/minStep >= numPts
541#
542def uascanFindFactor(start center finish numPts exponent minStep) '{
543  local factor fStep result f2 r2 i
544
545  factor = 0
546  result = uascanTestSeries(start, finish, numPts, factor, center, exponent, minStep)
547  if (result > 0) {
548    printf ("With factor=%g, could not get correct result (%g)\n", factor, result)
549    #
550    # fail gracefully with factor
551    # let calling routine decide what to do
552    # (usually just step with factor = 0 until x[i] > finish)
553    #
554    return (factor)
555  }
556  #
557  # Initially, choose factor = abs(finish - start) / (numPts - 1)
558  # call uascanTestSeries with factor
559  #  if result<0, then factor *= 10 and repeat
560  # then continue as below
561  #
562#  r2 = -1
563#  fStep = abs(finish-start) / (numPts -1)
564#  while (r2 < 0) {
565#    f2 = factor + fStep
566#    r2 = uascanTestSeries(start, center, finish, numPts, f2, exponent, minStep)
567#    if (uascanStepDebug >= 1)
568#      printf("factor = %g  result = %g\n", f2, r2)
569#    if (r2 < 0) fStep *= 10
570#  }
571  fStep = 10
572  #
573  # 40 times means better than 12-digit precision
574  #
575  for (i = 1; i < 40; i++) {
576    f2 = factor + fStep
577    r2 = uascanTestSeries(start, center, finish, numPts, f2, exponent, minStep)
578    if ( (r2 <= 0) && ( fabs(r2) < fabs(result) ) ) {
579      factor = f2
580      result = r2
581    } else {
582      fStep *= 0.5
583    }
584    if (uascanStepDebug >= 1)
585      printf ("%d: f=%0.15g  result=%0.15g\n", i, factor, result)
586    if ( fabs(result) < 0.5*fabs(minStep) ) break
587  }
588  return (factor)
589}'
590
591def _usaxs_triangulate (rot,center,dist) '{
592  local offset
593  offset = dist * tan((rot-center)*PI/180)
594  return(offset)
595}'
596
597
598
599
600#global     _n1     # number of intervals
601#global     _nm     # number of motors
602#global     _m[]    # motor number
603#global     _s[]    # start position
604#global     _f[]    # finish position
605#global     _d[]    # scale factor
606#global     _c[]    # center position
607#global     _ms[]   # minimum step size
608#global     _dy0    # photodiode Y position at center angle of scan
609#global     _ay0    # analyzer stage Y position at center angle of scan
610#global     _exp    # exponent for step function
611#global     _dir[]  # direction for motor to move
612#global     _pos[]  # present function (while step scanning)
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