MCA-1K Data Server Reference

MCA-1K

Introduction

USB driver

MCA-1K Device

Data structures

Overview

Module Constants

ARM Data structures

Version

Status

Controls

Calibration

Histogram

Time Histogram

Two-channel Logger

API

Overview

MCA-1K Data Structure: arm_status

Summary

The arm_status data structure reports data describing the current status of the slow-control system. Data reported include the count rates, alarm probabilities and more. Valid for PMT-based and SiPM-based MCA-1K devices such as PMT-1000, SiPM-1000.

Data structures

For arm_status these are the 'register' and 'field' data in use. All register data are 32-bit floats (float32).

arm_status registers and fields
Register number and field nameDescription
AS0: op_voltagePMT-1000: always 0. SiPM-1000 only: Current SiPM operating voltage; cf note 1.
AS1: target_voltReads arm_ctrl["cal_ov"] when gain stabilization is off; Reads a computed target voltage when gain stabilization is on; cf note 1.
AS2: set_voltagePMT-1000: always 0. SiPM-1000 only: Current operating voltage set by the DAC to achieve the op_voltage, cf note 1.
AS3: target_dgReads arm_ctrl["cal_dg"] when gain stabilization is off; Reads a computed target digital gain when gain stabilization is on; cf note 1. Reserved for future use.
AS4: cpu_temperatureCurrent ARM M0+ processor core temperature
AS5: x_temperaturePMT-1000: Current temperature of the high voltage unit. It is close to the PMT temperature. SiPM-1000: Current SiPM temperature measured by a sensor adjacent to the SiPM.
AS6: avg_temperatureCurrent temperature average (from selected sensor)
AS7: wall_clock time; Resolution is 65536/48MHz=1.365ms. Because these are float32 numbers delivered by the PMT-MCA, this field has only 23 mantissa bits and stops incrementing at 223; ie after 11453 s = 3.18 hours. (The field is repeated in the histogram data structure with full 32-bit precision, rolling over only after 67.9days.)
AS8: run_statusRun status, a bit-field.
AS8[0]: histo_activeIndicates if histogram acquisition is ongoing.
AS8[1]: alarm_activeIndicates if the alarming algorithm is active.
AS9: run_timeRun time of the foreground counter (resolution: 1.365333ms)
AS10: count_rateForeground or sample count rate
AS11: count_rate_errForeground count rate 2-σ error
AS12: run_time_bckRun time of the background counter (resolution: 1.365333ms)
AS13: count_rate_bckBackground count rate
AS14: count_rate_bck_errBackground count rate 2-σ error
AS15: count_rate_diffForeground minus background count rate
AS16: count_rate_diff_errForeground minus background count rate 2-σ error
AS17: background_probabilityProbability that the foreground counts are caused by the measured background rate.
AS18: bck_low_probabilityMost alarmist chance that the sample (S) is more radioactive than the background (B): P(counts > S+sigma(S) | B-sigma(B))
AS19: bck_high_probabilityMost cautious chance that the sample (S) is more radioactive than the background (B): P(counts > S-sigma(S) | B+sigma(B))
All arm_status registers and fields. Note 1: Parameter reads back zero when the lock-bit is set in arm_cal, LUT[63].
Sample - Background Counting Statistics
Illustration of alarm computation for the sample vs background measurement.

Below follow the time slice data entries for arm_status.

arm_status time slice results
NameDescription
AS20: ts_ready1→Time slice system is ready to generate alarms.
AS21: ts_alarm1→ There has been an alarm in the last ts_H time slices.
AS22: ts_netNet counts above background during the last L time slices
AS23: ts_bckBackground counts above background during the last L time slices
AS24: ts_probProbability that net is caused by the accepted background rate.
AS25: ts_resetTime slice counters were reset due to an extended alarm (longer than arm_ctrl["ts_H"])
arm_status time_slice fields

When comparing the activity of a sample against the background activity, the results will be reported in the fields shown below. The region of interest (ROI) is encoded in arm_ctrl at AC17, AC18: roi_low, roi_high.

arm_status sample vs background results
NameDescription
AS26: roi_rateSample count rate in the alarm ROI
AS27: roi_rate_err2-σ error for the above.
AS28: roi_rate_bckBackground count rate in the alarm ROI
AS29: roi_rate_bck_err2-σ error for the above.
AS30: roi_rate_diffSample - Background count rate in the alarm ROI
AS31: roi_rate_diff_err2-σ error for the above.
AS32: roi_eventsNumber of sample counts in the ROI during the sample acquisition time
AS33: roi_bckNumber of projected background counts in the ROI during the sample acquisition time.
Detailed arm_status sample vs background counting results
LED
NameDescription
AS34: led_valLED value, in MCA bins.
LED data for PMT-1000 that are equipped with an LED.

The 'user' dictionary for arm_status.

arm_status user dictionary
NameDescription
wall_clock_timeWall clock time in seconds; Resolution is 1.365ms.
counter_activeHistogram is updating; 0 or 1
active_bankNumber of the histogram bank that is updating; 0 or 1
arm_status 'user' dictionary entries