areaDetector Pilatus driver

January 21, 2018

Mark Rivers

University of Chicago

Table of Contents

Introduction

This is an EPICS areaDetector driver for the Pilatus pixel array detectors from Dectris.

The interface to the detector is via a TCP/IP socket interface to the camserver server that Dectris provides. The camserver program must be started before the areaDetector software is started, typically by running the camonly script provided by Dectris.

The camserver program saves the data to disk as TIFF or CBF files. The areaDetector software reads these disk files in order to read the data, because camserver does not provide another mechanism to access the data. If camserver is saving TIFF files then the driver reads the TIFFImageDescription tag from the TIFF file. This is a long string that camserver writes to the file containing all of the detector settings, including threshold, energy, etc. The driver adds this information to the NDArray using an NDAttribute called TIFFImageDescription. The NDFileTIFF plugin in ADCore R2-6 was changed to write this complete attribute to the TIFFImageDescription tag in the new TIFF file. It will also be written by the NDFileNetCDF, NDFileHDF5, and NDFileNexus plugins. However these plugins are currently limited to 256 character string attributes, so some of the information will be lost because the string is longer than 256 characters.

This driver inherits from ADDriver. It implements many of the parameters in asynNDArrayDriver.h and in ADArrayDriver.h. It also implements a number of parameters that are specific to the Pilatus detectors.The pilatusDetector class documentation describes this class in detail.

Implementation of standard driver parameters

The following table describes how the Pilatus driver implements some of the standard driver parameters.

Parameter Definitions in pilatusDetector.cpp and EPICS Record Definitions in pilatus.template
Parameter index variable EPICS record name Description
ADTriggerMode $(P)$(R)TriggerMode The driver redefines the choices for the ADTriggerMode parameter (record $(P)$(R)TriggerMode) from ADDriver.h. The choices for the Pilatus are:
  • Internal (external signal not used)
  • External Enable (count while external trigger line is high, readout on high to low transition)
  • External Trigger (begin acquisition sequence on high to low transition of external trigger line)
  • Multiple External Trigger (high to low transition on external signal triggers a single acquisition for the programmed exposure time)
  • Alignment (collect images as fast as exposure time and readout permit, images written to a temporary file)
The first 4 modes correspond directly to the camserver commands Exposure, ExtEnable, ExtTrigger, and ExtMTrigger respectively. Alignment mode uses the Exposure command as well, but continuously takes images into the same temporary file (alignment.tif).
ADAcquireTime $(P)$(R)AcquireTime Controls the acquisision time in all modes except External Enable. In External Enable mode the timing is controlled entirely by the external trigger line. However, even in ExternalEnable mode AcquireTime is used by camserver and by the driver to estimate how long the acquisition will take. Hardware timeouts will occur if the actual time to acquire differs significantly from the estimated time based on AcquireTime and AcquirePeriod.
ADNumImages $(P)$(R)NumImages Controls the number of images to acquire. It applies in all trigger modes except Alignment.
ADAcquirePeriod $(P)$(R)AcquirePeriod Controls the exposure period in seconds in Internal or External Trigger modes when NumImages >1. In External Enable mode the timing is controlled entirely by the external trigger line. However, even in ExternalEnable mode AcquirePeriod is used by camserver and by the driver to estimate how long the acquisition will take. Hardware timeouts will occur if the actual time to acquire differs significantly from the estimated time based on AcquireTime and AcquirePeriod.
ADNumExposures $(P)$(R)NumExposures Controls the number of exposures per image. It is most useful in External Enable mode, but it can be set in any mode.
ADAquire $(P)$(R)Acquire Controls the acquisition. Setting this to 1 starts image acquisition. The driver sets the record to 0 when acquisition is complete. This means an entire acquisition series if NImages >1. Setting this to 0 aborts an acquisition. If the driver was currently acquiring imges then this record will cause the "Stop" and "K" (Kill) commands to be sent to camserver.
NDFilePath $(P)$(R)FilePath Controls the path for saving images. It must be a valid path for camserver and for the areaDetector driver, which is normally running in an EPICS IOC. If camserver and the EPICS IOC are not running on the same machine then soft links will typically be used to make the paths look identical.
NDFileTemplate $(P)$(R)FileTemplate camserver uses the file extension to determine what format to save the files in. The areaDetector Pilatus driver only supports TIFF and CBF files, so the extension should be .tif or .cbf. When saving multiple images (NImages>1) camserver has its own rules for creating the names of the individual files. The rules are as follows. The name constructed using the algorithm described for NDFileTemplate under File Saving Parameters is used as a basename. The following examples show the interpretation of the basename.
Basename            Files produced
     
test6.tif           test6_00000.tif,  test6_00001.tif, ...
test6_.tif          test6_00000.tif,  test6_00001.tif, ...
test6_000.tif       test6_000.tif,    test6_001.tif, ...
test6_014.tif       test6_014.tif,    test6_015.tif, ...
test6_0008.tif      test6_0008.tif,   test6_0009.tif, ...
test6_2_0035.tif    test6_2_0035.tif, test6_2_0036.tif, ...
      
The numbers following the last '_' are taken as a format template, and as a start value. The minimum format is 3; there is no maximum; the default is 5. The format is also constrained by the requested number of images.

It is useful to load and enable an NDPluginStats plugin that gets its data from the Pilatus driver. The MaxValue_RBV PV for that plugin can be monitored to make sure that the 20-bit limit of 1,048,575 is not being approached in any pixel.

Pilatus specific parameters

The Pilatus driver implements the following parameters in addition to those in asynNDArrayDriver.h and ADDriver.h:. Note that to reduce the width of this table the parameter index variable names have been split into 2 lines, but these are just a single name, for example PilatusDelayTime.

Parameter Definitions in pilatusDetector.cpp and EPICS Record Definitions in pilatus.template
Parameter index variable asyn interface Access Description drvInfo string EPICS record name EPICS record type
Pilatus
DelayTime
asynFloat64 r/w Delay in seconds between the external trigger and the start of image acquisition. It only applies in External Trigger mode DELAY_TIME $(P)$(R)DelayTime ao
Pilatus
Threshold
asynFloat64 r/w Threshold energy in keV. camserver uses this value to set the discriminators in each pixel. It is typically set to the incident x-ray energy ($(P)$(R)Energy), but sometimes other values may be preferable. THRESHOLD $(P)$(R)ThresholdEnergy
$(P)$(R)ThresholdEnergy_RBV
ao
ai
Pilatus
ThresholdApply
asynInt32 r/w Apply the threshold value. Setting the threshold can be a time consuming operation, so if ThresholdAutoApply is No then ThresholdApply must be processed to actually send the threshold to camserver. THRESHOLD_APPLY $(P)$(R)ThresholdAppply busy
Pilatus
ThresholdApply
asynInt32 r/w Apply the threshold value. Setting the threshold can be a time consuming operation, so if ThresholdAutoApply is No then ThresholdApply must be processed to actually send the threshold to camserver. THRESHOLD_APPLY $(P)$(R)ThresholdApply busy
Pilatus
ThresholdAutoApply
asynInt32 r/w Automatically apply the threshold value whenever it changes. Setting the threshold can be a time consuming operation, so if ThresholdAutoApply is No then ThresholdApply must be processed to actually send the threshold to camserver. If it is Yes then the threshold value will be sent to camserver whenever it is changed. THRESHOLD_AUTO_APPLY $(P)$(R)ThresholdAutoApply
$(P)$(R)ThresholdAutoApply_RBV
bo
bi
Pilatus
Energy
asynFloat64 r/w X-ray energy in keV. This is used by camserver to calculate the proper flat field corrrection. If Energy is 0 then the energy value sent to camserver is ThresholdEnergy*2. ENERGY $(P)$(R)Energy
$(P)$(R)Energy_RBV
ao
ai
Pilatus
GapFill
asynInt32 r/w The value that camserver should write to the data file for the gaps between pixels in the detector. Choices are -2, 0, and -1. GAP_FILL $(P)$(R)GapFill
$(P)$(R)GapFill_RBV
mbbo
mbbi
N/A N/A r/w Gain menu. Controls the value of Vrf, which determines the shaping time and gain of the input amplifiers. The allowed values are:
  • 0 ("Fast/Low") Fastest shaping time (~125ns) and lowest gain.
  • 1 ("Medium/Medium") Medium shaping time (~200 ns) and medium gain.
  • 2 ("Slow/High") Slow shaping time (~400 ns) and high gain.
  • 3 ("Slow/Ultrahigh") Slowest peaking time (? ns) and highest gain.
This is only used on older Pilatus detectors, not the newer ones.
N/A $(P)$(R)GainMenu mbbo
Pilatus
Armed
asynInt32 r/o Flag to indicate when the Pilatus is ready to accept external trigger signals (0=not ready, 1=ready). This should be used by clients to indicate when it is OK to start sending trigger pulses to the Pilatus. If pulses are send before Armed=1 then the Pilatus may miss them, leading to DMA timeout errors from camserver ARMED $(P)$(R)Armed bi
Pilatus
ResetPower
asynInt32 r/w Processing this record sends the "ResetModulePower delayTime" command to camserver. This cycles the high voltage and other detector supply voltages. This is particularly useful with the CdTe detectors when they have been exposed to a very strong signal. Cycling the power can erase the memory effects of oversaturation. The delayTime controls the amount of time to wait after turning off the power before turning it back on again. It is set by the ResetPowerTime record. RESET_POWER $(P)$(R)ResetPower bo
Pilatus
ResetPowerTime
asynInt32 r/w This record controls the number of seconds to wait after turning off the power before turning it back on again when the ResetPower record is processed. RESET_POWER_TIME $(P)$(R)ResetPower
$(P)$(R)ResetPower_RBV
bo
bi
PilatusImage
FileTmot
asynFloat64 r/w Timeout in seconds when reading a TIFF or CBF file. It should be set to several seconds, because there can be delays for various reasons. One reason is that there is sometimes a delay between when an External Enable acquisition is started and when the first external pulse occurs. Another is that it can take some time for camserver processes to finish writing the files. IMAGE_FILE_TMOT $(P)$(R)ImageFileTmot ao
Pilatus
BadPixelFile
asynOctet r/w Name of a file to be used to replace bad pixels. If this record does not point to a valid bad pixel file then no bad pixel mapping is performed. The bad pixel map is used before making the NDArray callbacks. It does not modify the data in the files that camserver writes. This is a simple ASCII file with the following format:
badX1,badY1 replacementX1,replacementY1 
badX2,badY2 replacementX2,replacementY2
...
          
The X and Y coordinates range from 0 to NXPixels-1 and NYPixels-1. Up to 100 bad pixels can be defined. The bad pixel mapping simply replaces the bad pixels with another pixel's value. It does not do any averaging. It is felt that this is sufficient for the purpose for which this driver was written, namely fast on-line viewing of ROIs and image data. More sophisticated algorithms can be used for offline analysis of the image files themselves. The following is an example bad pixel file for a GSECARS detector:
          
263,3   262,3
264,3   266,3
263,3   266,3
300,85  299,85
300,86  299,86
471,129 472,129
          
BAD_PIXEL_FILE $(P)$(R)BadPixelFile waveform
Pilatus
NumBadPixels
asynInt32 r/o The number of bad pixels defined in the bad pixel file. Useful for seeing if the bad pixel file was read correctly. NUM_BAD_PIXELS $(P)$(R)NumBadPixels longin
Pilatus
FlatFieldFile
asynOctet r/w Name of a file to be used to correct for the flat field. If this record does not point to a valid flat field file then no flat field correction is performed. The flat field file is simply a TIFF or CBF file collected by the Pilatus that is used to correct for spatial non-uniformity in the response of the detector. It should be collected with a spatially uniform intensity on the detector at roughly the same energy as the measurements being corrected. When the flat field file is read, the average pixel value (averageFlatField) is computed using all pixels with intensities >PilatusMinFlatField. All pixels with intensity <PilatusMinFlatField in the flat field are replaced with averageFlatField. When images are collected before the NDArray callbacks are performed the following per-pixel correction is applied:
ImageData[i] = 
    (averageFlatField * 
    ImageData[i])/flatField[i];
          
FLAT_FIELD_FILE $(P)$(R)FlatFieldFile waveform
Pilatus
MinFlatField
asynInt32 r/w The mimimum valid intensity in the flat field. This value must be set > 0 to prevent divide by 0 errors. If the flat field was collected with some pixels having very low intensity then this value can be used to replace those pixels with the average response. MIN_FLAT_FIELD $(P)$(R)MinFlatField longout
Pilatus
FlatFieldValid
asynInt32 r/o This record indicates if a valid flat field file has been read. 0=No, 1=Yes. FLAT_FIELD_VALID $(P)$(R)FlatFieldValid bi
Pilatus
Wavelength
asynFloat64 r/w MX wavelength to write to CBF and TIFF image header. WAVELENGTH $(P)$(R)Wavelength ao
Pilatus
EnergyLow
asynFloat64 r/w MX energy range low value to write to CBF and TIFF image header. ENERGY_LOW $(P)$(R)EnergyLow ao
Pilatus
EnergyHigh
asynFloat64 r/w MX energy range high value to write to CBF and TIFF image header. ENERGY_HIGH $(P)$(R)EnergyHigh ao
Pilatus
DetDist
asynFloat64 r/w MX detector distance to write to CBF and TIFF image header. DET_DIST $(P)$(R)DetDist ao
Pilatus
DetVOffset
asynFloat64 r/w MX detector vertical offset to write to CBF and TIFF image header. DET_VOFFSET $(P)$(R)DetVOffset ao
Pilatus
BeamX
asynFloat64 r/w MX beam X to write to CBF and TIFF image header. BEAM_X $(P)$(R)BeamX ao
Pilatus
BeamY
asynFloat64 r/w MX beam Y to write to CBF and TIFF image header. BEAM_Y $(P)$(R)BeamY ao
Pilatus
Flux
asynFloat64 r/w MX flux to write to CBF and TIFF image header. FLUX $(P)$(R)Flux ao
Pilatus
FilterTransm
asynFloat64 r/w MX filter transmission to write to CBF and TIFF image header. FILTER_TRANSM $(P)$(R)FilterTransm ao
Pilatus
StartAngle
asynFloat64 r/w MX start angle to write to CBF and TIFF image header. When saving multiple images (ADNumImages>1) camserver will automatically increment the field in the image header by PilatusAngleIncr for each image. START_ANGLE $(P)$(R)StartAngle ao
Pilatus
AngleIncr
asynFloat64 r/w MX angle increment to write to CBF and TIFF image header. When saving multiple images (ADNumImages>1) camserver will automatically increment the field corresponding to PilatusStartAngle in the image header by this value for each image. ANGLE_INCR $(P)$(R)AngleIncr ao
Pilatus
Det2theta
asynFloat64 r/w MX detector 2theta to write to CBF and TIFF image header. DET_2THETA $(P)$(R)Det2theta ao
Pilatus
Polarization
asynFloat64 r/w MX polarization to write to CBF and TIFF image header. POLARIZATION $(P)$(R)Polarization ao
Pilatus
Alpha
asynFloat64 r/w MX alpha to write to CBF and TIFF image header. ALPHA $(P)$(R)Alpha ao
Pilatus
Kappa
asynFloat64 r/w MX kappa to write to CBF and TIFF image header. KAPPA $(P)$(R)Kappa ao
Pilatus
Phi
asynFloat64 r/w MX phi to write to CBF and TIFF image header. PHI $(P)$(R)Phi ao
Pilatus
PhiIncr
asynFloat64 r/w MX phi increment to write to CBF and TIFF image header PHI_INCR $(P)$(R)PhiIncr ao
Pilatus
Chi
asynFloat64 r/w MX chi to write to CBF and TIFF image header. CHI $(P)$(R)Chi ao
Pilatus
ChiIncr
asynFloat64 r/w MX chi increment to write to CBF and TIFF image header CHI_INCR $(P)$(R)ChiIncr ao
Pilatus
Omage
asynFloat64 r/w MX omega to write to CBF and TIFF image header. OMEGA $(P)$(R)Omega ao
Pilatus
OmegaIncr
asynFloat64 r/w MX omega increment to write to CBF and TIFF image header OMEGA_INCR $(P)$(R)OmegaIncr ao
Pilatus
OscillAxis
asynOctet r/w MX oscillation axis text, up to 18 characters in length, to write to CBF and TIFF image header. OSCILL_AXIS $(P)$(R)OscillAxis stringout
Pilatus
NumOscill
asynInt32 r/w MX number of oscillations to write to CBF and TIFF image header. NUM_OSCILL $(P)$(R)NumOscill longout
Pilatus
CbfTemplateFile
asynOctet r/w Template file to be used to obtain all of the MX parameters above. Set the name of this file to "0" to disable the template file. CBFTEMPLATEFILE $(P)$(R)CbfTemplateFile waveform
Pilatus
HeaderString
asynOctet r/w Header string to write in the COMMENT field of the CBF file. HEADERSTRING $(P)$(R)HeaderString waveform
Pilatus
PixelCutoff
asynInt32 r/o Maximum possible count rate per pixel. PIXEL_CUTOFF $(P)$(R)PixelCutOff_RBV ai
Pilatus
ThTemp0
asynFloat64 r/o Temperature readout 0. TH_TEMP_0 $(P)$(R)Temp0_RBV ai
Pilatus
ThTemp1
asynFloat64 r/o Temperature readout 1. TH_TEMP_1 $(P)$(R)Temp1_RBV ai
Pilatus
ThTemp2
asynFloat64 r/o Temperature readout 2. TH_TEMP_2 $(P)$(R)Temp2_RBV ai
Pilatus
ThHumid0
asynFloat64 r/o Humidity readout 0. TH_HUMID_0 $(P)$(R)Humid0_RBV ai
Pilatus
ThHumid1
asynFloat64 r/o Humidity readout 1. TH_HUMID_1 $(P)$(R)Humid1_RBV ai
Pilatus
ThHumid2
asynFloat64 r/o Humidity readout 2. TH_HUMID_2 $(P)$(R)Humid2_RBV ai
Pilatus
TvxVersion
asynOctet r/o Version of TVX and camserver. This record is redundant with the SDKVersion_RBV record added in ADCore R2-6, which should be used instead. TVXVERSION $(P)$(R)TVXVersion_RBV stringin
N/A N/A N/A asyn record to control debugging communication with camserver. Setting the CNCT field in this record to Disconnect causes the drvAsynIPPort server to disconnect from camserver. This can be used to allow another program, such as TVX, to temporarily take control of camserver, without restarting the EPICS IOC. Set CNCT to Connect to reconnect the IOC to camserver, or simply process any record which communicates with camserver, because the driver will automatically reconnect. N/A $(P)$(R)CamserverAsyn asyn

Configuration

The pilatusDetector driver is created with the pilatusDetectorConfig command, either from C/C++ or from the EPICS IOC shell.

int pilatusDetectorConfig(const char *portName, const char *camserverPort, 
                          int maxSizeX, int maxSizeY,
                          int maxBuffers, size_t maxMemory,
                          int priority, int stackSize)
  

For details on the meaning of the parameters to this function refer to the detailed documentation on the pilatusDetectorConfig function in the pilatusDetector.cpp documentation and in the documentation for the constructor for the pilatusDetector class.

There an example IOC boot directory and startup script (iocBoot/iocPilatus/st.cmd) provided with areaDetector.

MEDM screens

The following show the MEDM screens that are used to control the Pilatus detector. Note that the general purpose screen ADBase.adl can be used, but it exposes many controls that are not applicable to the Pilatus.

pilatusDetector.adl is the main screen used to control the Pilatus driver.

pilatusDetector.adl

pilatusDetector.png

pilatusAncillary.adl is the screen used to control define the metadata that will be written to the Pilatus data file.

pilatusAncillary.adl

pilatusAncillary.png

NDROI4.adl is used to define the ROIs. In this example there are 3 valid ROIs defined. ROI 1 is the entire detector, ROI 2 is a 300x50 rectangle starting at [100,60], and ROI 3 is a 50x30 rectangle starting at [220,70].

NDROI4.adl

pilatusROI4.png

NDStats5.adl is used to display the statistics in the ROIs defined above.

NDStats5.adl

pilatusStats5.png

mca.adl or mca_small.adl can be used to plot the net or total counts in an ROI when NImages>1. In this example the plot is the net counts in ROI 1 as the diffractometer chi was scanned +- 1 degree with 1000 points at .02 seconds/point. This was done with the SPEC command

lup chi -1 1 1000 .02

using trajectory scanning on a Newport kappa diffractometer. This was a compound motor scan with the Newport XPS putting out pulses every .02 seconds. These pulses triggered the Pilatus in External Enable mode. The Pilatus driver read each TIFF file as it was created and updated this plot every 0.2 seconds. The total time to collect this scan with 1000 images was 20.8 seconds.

mca_small.adl

pilatusMCA.png

scan_more.adl is used to define a scan. In this example the sscan record is set up to scan the ThresholdEnergy PV and to collect the total counts in ROI2, which was defined to include the entire detector.

scan_more.adl

pilatusThresholdScanSetup.png

scanDetPlot.adl is used to plot the results of a scan after it is complete. In this example the total counts in ROI 1 are plotted as a function of the ThresholdEnergy as it was scanned from 3000 to 10000 eV in 250 eV steps. The source was Fe55, and the cut-off is at 6 keV, as expected for the Mn Ka and Mn Kb x-rays that this source produces.

scanDetPlot.adl

pilatusThresholdScanPlot.png

asynRecord.adl is used to control the debugging information printed by the asyn TCP/IP driver for camserver (asynTraceIODriver).

asynRecord.adl

pilatusAsyn.png

asynOctet.adl can be used to send any command to camserver and display the response. It can be loaded from the More menu in asynRecord.adl above.

asynOctet.adl

pilatusAsynOctet.png

SPEC interface

At the GSECARS beamlines (13-ID-C and 13-BM-C) at the APS we use SPEC to control our Newport diffractometers. We have added and modified SPEC macros to use the pilatusDetector areaDetector driver to treat the Pilatus detector as a SPEC counter. This works in both traditional step-scanning mode, as well as in trajectory scanning mode. Here are some snippets from the SPEC macros for the Pilatus. We can supply the source files on request.

  # need some more globals (kludge)
global    PILATUS_ROI_PV   
global    PILATUS_ROI_ARRAY_PV 
global    PILATUS_ROI_ARRAY_START_PV
global    PILATUS_ROI_ARRAY_NUSE_PV
global    PILATUS_ROI_ARRAY_ACQ_PV
global    PILATUS_IMGPATH_PV
global    PILATUS_FNAME_PV
global    PILATUS_FILENUMBER_PV
global    PILATUS_FILEFORMAT_PV
global    PILATUS_EXPSRTM_PV
global    PILATUS_NFRAME_PV
global    PILATUS_EXPPRD_PV
global    PILATUS_NEXPFRM_PV
global    PILATUS_ACQ_PV
global    PILATUS_ARMED_PV
global    PILATUS_ABORT_PV
global    PILATUS_ACQMODE_PV
global    PILATUS_READOUT_TIME

global    PILATUS_ROI_0_MinX_PV
global    PILATUS_ROI_0_SizeX_PV
global    PILATUS_ROI_0_MinY_PV
global    PILATUS_ROI_0_SizeY_PV


###############################################################
def _setup_img '{
...          
     # PILATUS_PREFIX detector name i.e. (GSE-PILATUS1:)
     if ( PILATUS_PREFIX == "") PILATUS_PREFIX = "GSE-PILATUS1:"
     PILATUS_PREFIX = getsval("Enter PILATUS detector name i.e. GSE-PILATUS1:",PILATUS_PREFIX)

     # PILATUS_DET_PREFIX is the pv used by areaDetector to identify a specific detector.
     # When only one detector is used it is usally (cam1:)
     if ( PILATUS_DET_PREFIX == "") PILATUS_DET_PREFIX = "cam1:"
     PILATUS_DET_PREFIX = getsval("Enter PILATUS specific detector name i.e. cam1:",PILATUS_DET_PREFIX)

     # PILATUS_ROI_PREFIX is the pv used by areaDetector to identify a specific a ROI plugin.
     # When only one ROI plugin is used it is usally (ROI1:)
     if ( PILATUS_ROI_PREFIX == "") PILATUS_DET_PREFIX = "ROI1:"
     PILATUS_ROI_PREFIX = getsval("Enter PILATUS ROI plugin name i.e. ROI1:",PILATUS_ROI_PREFIX)
     
     if (PILATUS_MOUNT == "") PILATUS_MOUNT = "cars5/Data"
     PILATUS_MOUNT = getsval("Enter mount point relative to camserver home directory",PILATUS_MOUNT)
     if (PILATUS_SPEC_MOUNT == "") PILATUS_SPEC_MOUNT = "cars5/Data"
     PILATUS_SPEC_MOUNT = getsval("Enter mount point relative to spec home directory",PILATUS_SPEC_MOUNT) 
...
     PILATUS_ROI_PV             = PILATUS_PREFIX PILATUS_ROI_PREFIX "0:Net_RBV"
     PILATUS_ROI_ARRAY_PV       = PILATUS_PREFIX PILATUS_ROI_PREFIX "0:NetArray"
     PILATUS_ROI_ARRAY_START_PV = PILATUS_PREFIX PILATUS_ROI_PREFIX "0:NetArrayEraseStart"
     PILATUS_ROI_ARRAY_NUSE_PV  = PILATUS_PREFIX PILATUS_ROI_PREFIX "0:NetArray.NUSE"
     PILATUS_ROI_ARRAY_ACQ_PV   = PILATUS_PREFIX PILATUS_ROI_PREFIX "0:NetArray.ACQG"
     PILATUS_IMGPATH_PV         = PILATUS_PREFIX PILATUS_DET_PREFIX "FilePath"
     PILATUS_FNAME_PV           = PILATUS_PREFIX PILATUS_DET_PREFIX "FileName"
     PILATUS_FILENUMBER_PV      = PILATUS_PREFIX PILATUS_DET_PREFIX "FileNumber"
     PILATUS_FILEFORMAT_PV      = PILATUS_PREFIX PILATUS_DET_PREFIX "FileTemplate"
     PILATUS_EXPSRTM_PV         = PILATUS_PREFIX PILATUS_DET_PREFIX "AcquireTime"
     PILATUS_NFRAME_PV          = PILATUS_PREFIX PILATUS_DET_PREFIX "NumImages"
     PILATUS_EXPPRD_PV          = PILATUS_PREFIX PILATUS_DET_PREFIX "AcquirePeriod"
     PILATUS_NEXPFRM_PV         = PILATUS_PREFIX PILATUS_DET_PREFIX "NumExposures"
     PILATUS_ACQ_PV             = PILATUS_PREFIX PILATUS_DET_PREFIX "Acquire"
     PILATUS_ARMED_PV           = PILATUS_PREFIX PILATUS_DET_PREFIX "Armed"
     PILATUS_ABORT_PV           = PILATUS_PREFIX PILATUS_DET_PREFIX "Acquire"
     PILATUS_ACQMODE_PV         = PILATUS_PREFIX PILATUS_DET_PREFIX "TriggerMode"
     PILATUS_THRESHOLD_PV       = PILATUS_PREFIX PILATUS_DET_PREFIX "ThresholdEnergy"
     PILATUS_ROI_0_MinX_PV      = PILATUS_PREFIX PILATUS_ROI_PREFIX "0:MinX"
     PILATUS_ROI_0_SizeX_PV     = PILATUS_PREFIX PILATUS_ROI_PREFIX "0:SizeX"
     PILATUS_ROI_0_MinY_PV      = PILATUS_PREFIX PILATUS_ROI_PREFIX "0:MinY"
     PILATUS_ROI_0_SizeY_PV     = PILATUS_PREFIX PILATUS_ROI_PREFIX "0:SizeY"
     PILATUS_ROI_0_BgdWidth_PV  = PILATUS_PREFIX PILATUS_ROI_PREFIX "0:BgdWidth"
...

def epics_pilatus_count '{
...
     # Call macro that creates and set the Pilatus path and filename
     img_full_filename

     # Setup exposure time, collection mode and number of frames
     epics_put(PILATUS_FILENUMBER_PV,NPTS, 1)
     epics_put(PILATUS_NFRAME_PV, 1, 1)
     epics_put(PILATUS_ACQMODE_PV,0, 1)  # Internal trigger
     epics_put(PILATUS_EXPSRTM_PV,cnt_time_val, 1)
     epics_put(PILATUS_NEXPFRM_PV, 1, 1)

...
     # hit the triggers
     epics_put(PILATUS_ACQ_PV,1)

     epics_put(sc_cnt_pv,1)

     # wait for scaler and Pilatus AQG to finish
     status     = 1
     sc_done    = FALSE
     img_done   = FALSE
     data_done  = FALSE
     while(status){
         # is the scalar done
        if (epics_get(sc_cnt_pv)=="Done"){
             sc_done = TRUE;
             #p "scaler done"
        }

        # is the pilatus done
        if (epics_get(PILATUS_ACQ_PV) == "Done"){
            img_done = TRUE;
            #p "image collection done"
        }

        if( (sc_done==TRUE) && (img_done==TRUE)) break;
        sleep(0.01)
     }

    
     # use the get_counts routine to read the scalers
     # note get_counts also calls user_getcounts
     # thats where the rois get read.
     get_counts  
}'


def user_getcounts '{
...
    # using image_count routine
    } else if ( EPICS_COUNT == 4 ) {
        S[iroi] = 0
        S[iroi] = epics_get(PILATUS_ROI_PV)

Performance measurements

The following measurements were done to demonstrate the performance that can be obtained with the areaDetector Pilatus driver.

  1. AcquireMode=Internal, NumImages=1000, AcquireTime=.005, AcquirePeriod=.01, NumExposures=1. The time to collect this series should be exactly 10.0 seconds. The actual time was measured using the EPICS camonitor program. It printed the time when acquisition was started (Acquire changed to Acquire=1) and when acquisition was complete (Acquire changed to Done=0). The time was 10.022 seconds. This includes the time for camserver to save all 1000 images to disk (366 MB), and for the driver to read each file, correct the bad pixels and flat field, compute the ROIs, and post the ROIs to EPICS. It also posted all of the images to EPICS. The total additional time was less than 0.03 seconds for all 1000 images.
  2. AcquireMode=Internal, NImages=1, ExposureTime=.01, NExposures=1. An EPICS sscan record was used to collect 1000 points. There were no positioner PVs (to eliminate motor overhead). The only detector trigger was the Pilatus Acquire PV. The only detector PV was ROI1:0:Total_RBV. In this mode camserver is being told to individually collect each file. If there were no overhead then time to collect this series should be exactly 10.0 seconds. The actual time measured using the EPICS camonitor program was 45.514 seconds. The overhead is thus 35.514 seconds, or 35 ms per point. In this single-frame mode the driver is thus able to collect >20 images/second. For comparison, another measurement was done using the same EPICS sscan record, but using a Joerger VSC16 scaler as the detector trigger and detector. The preset time was also .01 seconds. The elapsed time for a 1000 point scan was 16.068 seconds, so the overhead was 6.068 seconds, or 6 ms per point.
  3. AcquireMode=Ext. Enable, NImages=1000, NExposures=1. SPEC was used to collect 1000 points using trajectory scanning mode with the Newport XPS motor controller. The following SPEC command was used:
          lup chi -1 1 1000 .02
          
    This tells SPEC to do a relative scan of the chi axis from -2 degrees to +2 degrees with 1000 points at .015 seconds/point. On our kappa diffractometer this entails a coordinated motion of the phi, kappa and omega axes. The EPICS trajectory scanning software downloads the non-linear trajectory that SPEC computes into the XPS controller, which executes it. As the motors are moving the XPS outputs synchronization pulses at the period of the collection time, .020 seconds in this case. These pulses are used as the external trigger to the Pilatus. The time to execute this scan should be 20.0 seconds. The actual time was 20.8 seconds, measured using camonitor on the Acquire PV. Again, this includes the time for camserver to save all 1000 images to disk (366 MB), and for the Pilatus driver to read each file, correct the bad pixels and flat field, compute the ROIs, and post the ROIs to EPICS. It also posted all of the images to EPICS. The total additional time was less than 0.8 seconds for all 1000 images. As soon as the acquisition was complete SPEC plotted the net counts in the first ROI (containing the Bragg peak) as follows:

    1000 point SPEC scan with 20 ms per point collected in 20.8 seconds

    pilatusSPEC.png

    For comparison this identical scan was executed in traditional step-scanning mode, where the motors stopped at each point in the scan. The Pilatus was run in Internal mode with NumImages=1. The total time for the scan was 870 seconds (more than 14 minutes), compared to 20.8 seconds in trajectory mode. Most of this overhead is the settling time for the motors, with only a small fraction due to the Pilatus single-exposure mode. The trajectory scanning mode is thus more than 50 times faster to execute the identical SPEC scan.

Hardware notes

Trigger pulses

The Pilatus supports 3 types of external triggering. In External Trigger mode (the camserver ExtTrigger command) the Pilatus uses the programmed values of AcquireTime, AcquirePeriod, NImages and NExposures. It waits for a single external trigger, then waits for Delay seconds and then collects the entire sequence. It is very similar to Internal mode with NImages>1, except that it waits for a trigger to begin collecting the sequence.

In External Enable mode (the camserver ExtEnable command) the Pilatus uses the external signal to control acquisition. Only NImages and NExposures are used, AcquireTime and AcquirePeriod are not used. When the signal is high the detector counts, and on the transition to low it begins its readout.

In External MultiTrigger Mode (the camserver ExtMTrigger command) the Pilatus uses the programmed AcquireTime, in addition to NImages and NExposures. Each external trigger pulse causes the Pilatus to collect one image at the programmed exposure time. This mode works well with a trigger source like the Newport motor controllers or the SIS380x multichannel scaler, that put out a short trigger pulse for each image. One only needs to take care that the time between external trigger pulses is at least 4msec longer than the programmed exposure time, to allow time for the detector to read out before the next trigger pulse arrives.

When using the External Enable mode, we use an inexpensive analog pulse generator to convert the trigger pulses from the MM4005 and XPS to a form suitable for External Enable mode with the Pilatus. This is the solution we have developed that seems to be reliable:

The Tenma TGP110 seems to be currently called a Tenma 72-6860, and lists for about $350 new at Newark.

Detector Voltage

When we were initially testing the Pilatus in the lab, we had many errors in External Enable mode, where it did not seem to be seeing the external pulses. camserver would get DMA timeouts, and need to be restarted. Dectris said these were happening because the cables on our detector are longer than normal, and the voltage drop from the power supply to the detector was leading to marginal voltage values. They suggested shortening the cables or increasing the supply voltage slightly. When moving the detector to the hutch these problems initially went away. However, they then recurred, and we fixed the problem by increasing the power supply voltage from 4.4 to 4.7 volts at the detector.

Dectris has since informed me that they have increased the power supply voltage on all new Pilatus systems, so this should no longer be an issue.

Restrictions

The following are some current restrictions of the areaDetector Pilatus driver: