Update Hit Finding Algorithm #8
Description
Below are the description of pulsing finding for the IWCD mPMTs. We will need to implement it in the waveform fitting function to get digitized Q and T.
The general description of the hit finding algorithm was shown in the presentation on the meeting on 15 February 2024. Here is this description:
- Self-trigger is verified and triggering conditions are as follows:
- Amplitude exceeding the threshold
- Integral of 7 samples (preceding and following) exceeds 2x threshold
- Local maximum
- Sufficient period from the previous pulse
- FIFOs are not almost full – to prevent overflow
- Waveform windows includes eight samples before maximum
- Window length is configurable
- Positive polarity
- Time is estimated using Constant Fraction Discriminator (CFD) for subsequent windows
- Charge is estimated as the sum of eight samples around the maximum.
The extraction of related VHDL code is attached.
constant SAMPLE_NUMBER_BEFORE_MAXIMUM : natural := 8;-- first sample number before
constant SAMPLE_NUMBER_AFTER_MAXIMUM : natural := 7;--namber of samples after maximum kept in pipeline registers
constant INTEGRAL_PRECEDING_SAMPLE_NUMBER : natural := 2;
constant INTEGRAL_FOLLOWING_SAMPLE_NUMBER : natural := 4;
---------------------------------------------------------------
---- selected VHDL code describing the hit detection ----------
adder_tree_v := (others => (others => (others => '0')));
for channel in 0 to 19 loop
-- integral computation using adder tree on moving window
for i in SAMPLE_NUMBER_AFTER_MAXIMUM-1-INTEGRAL_PRECEDING_SAMPLE_NUMBER to SAMPLE_NUMBER_AFTER_MAXIMUM-1+INTEGRAL_FOLLOWING_SAMPLE_NUMBER loop
adder_tree_v(channel)(i+3-SAMPLE_NUMBER_AFTER_MAXIMUM) := adc_delay_r(i)(channel)(11) & adc_delay_r(i)(channel)(11) & adc_delay_r(i)(channel)(11) & adc_delay_r(i)(channel);
end loop;
-- first adder level
for i in 0 to 3 loop
adder_tree_v(channel)(i+8) := adder_tree_v(channel)(2*i) + adder_tree_v(channel)(2*i+1);
end loop;
adder_tree_v(channel)(12) := adder_tree_v(channel)(8) + adder_tree_v(channel)(9);
adder_tree_v(channel)(13) := adder_tree_v(channel)(10) + adder_tree_v(channel)(11);
adder_tree_v(channel)(14) := adder_tree_v(channel)(12) + adder_tree_v(channel)(13);
sum_v(channel) := adder_tree_v(channel)(14) & "00";
trigger_auto_v(channel) := '0';
if signed(adc_delay_r(SAMPLE_NUMBER_AFTER_MAXIMUM-1)(channel)) >= signed(adc_delay_r(SAMPLE_NUMBER_AFTER_MAXIMUM-2)(channel))
and signed(adc_delay_r(SAMPLE_NUMBER_AFTER_MAXIMUM-1)(channel)) > signed(adc_delay_r(SAMPLE_NUMBER_AFTER_MAXIMUM)(channel))
and signed(adc_delay_r(SAMPLE_NUMBER_AFTER_MAXIMUM-1)(channel)) > signed(adc_delay_r(SAMPLE_NUMBER_AFTER_MAXIMUM-3)(channel))
and signed(adc_delay_r(SAMPLE_NUMBER_AFTER_MAXIMUM-1)(channel)) > signed(adc_delay_r(SAMPLE_NUMBER_AFTER_MAXIMUM+1)(channel))
then
maximum_condition_v(channel) := '1';
end if;
if signed(adc_delay_r(SAMPLE_NUMBER_AFTER_MAXIMUM-1)(channel)) > signed(integral_threshold_v(11 downto 3)) then
amplitude_condition_v(channel) := '1';
end if;
if signed(sum_v(channel)) > signed(integral_threshold_v) then
integral_condition_v(channel) := '1';
end if;
if estimator_r(channel).cycles_from_hit = 0 or estimator_r(channel).cycles_from_hit > config_r.hit_insensitivity_period then
separation_condition_v(channel) := '1';
end if;
end loop;
trigger_auto_v := maximum_condition_v and integral_condition_v and amplitude_condition_v and separation_condition_v and config_r.self_trigger_enable;