# First look at TOF calibration

From GlueXWiki

### First Look

- first select data sample with the following conditions:
- only consider hits within 50ns of the timing peak both for ADC data and TDC data
- only consider paddles that have hits on both ends
- take care of the 6fold trigger timing shift in the TDC (24ns window)

- Do a rough determination of the walk correction by using the time in the ADC as reference.

- Do mean time comparison between different planes
- calculate MeanTime of Paddle i in plane j:
- calculate MeanTime for all Paddles n in plane k:
- For each Reference paddle in plane j:
- and after using the correct timing conversion of 23.4375ps/bin:
- Fit the meant time peak of each projection. This is the relative mean-time difference.
- example 1
- example 2
- and now a good example after using the correct timing conversion
- and an example where the automatic fit failed because the meantime peak is smaller than the background
- Do this for each paddle in the first plane as reference paddle.
- Choose one paddle in the first plane as THE REFERENCE PADDLE
- Calculate the difference between the fit results of each paddle in the first plane w.r.t. THE REFERENCE PADDLE and fit the distribution
- average difference of mean time to REFERENCE PADDLE
- Now we have offsets for the Mean-Time for all Paddles w.r.t. THE REFERENCE PADDLE

- Do time difference comparison of one paddle with the paddle number in the other plane
- calculate time difference:
- plot this time difference vs. paddle number of paddles that got hit in the other plane
- again look at each projection and fit the peak
- example fits
- now one can also plot the fit results as a function of paddle number. The inverse slope is the speed module paddle pitch
- one can also plot the difference between symmetric paddles around the beam hole
- choose the intersection at zero for the time difference offset

- Now we have offsets for time difference (TD) and mean time (MT)
- offset for the left pmt:
- offset for the right pmt:
- as a bonus we get the effective speed of light for each paddle.