LHC's New Chip Tackles Radiation Challenges
12 comments
·August 10, 2025magicalhippo
SiempreViernes
Pretty sure they measured the pulse and fitted a function to describe it themselves, its not like the bought the scintillator on Alibaba and it happened to come with a spec sheet listing the analytical form.
magicalhippo
Seems you're right[1]:
LAr cells pulse shapes can be predicted from calibration pulses by several models such as Response Transformation Method (RTM) and First Principles Method (FPM). Both model requires that the drift time be measured.
[1]: https://inspirehep.net/files/cb39822f5ead85e84d7a1221bcd68fa...
null
hinkley
I’m shocked that’s a high enough sampling rate.
tux3
That's actually a design parameter! The particles circulate in the ring in a series of bunches, and they're spaced apart so that bunches collide at 40MHz
So the particles aren't colliding continously, they're injected and collided bunch by bunch
hinkley
So the clock skew is high resolution but the clock rate is low. Makes sense.
brcmthrowaway
Maybe they use aliasing?
thrance
Title of the article starts with "Large Hardon Collider". I can't think of anything quippy to add, but that's not how "Hadron" is spelled.
HPsquared
I'm often amused to see what an individual's personally-tuned keyboard app / spellcheck outputs. It's a bit of an information leak sometimes!
pstuart
They really pulled a boner there.
null
I was curious about the analog to digital converter stages, and how it would fare in the radiation.
Turns out they're a bit lucky I guess. As noted in the paper[1]:
Transient errors affecting one or a few data samples due to SEUs can be tolerated and corrected by offline data analysis since the LAr pulse shape is analytically known.
This was used in their design:
The architecture incorporates a 9-subrange (3.2 bits) MDAC before a 12-bit, two-stage SAR, with the MDAC used to relax the dynamic range requirement for the SAR.
The MDAC and SAR are memory-less and their states are determined by the 40-MHz precision sampling clock and an intermediate 80-MHz internal clock signal. Therefore, any radiation-induced upset will only affect an individual sample.
[1]: https://ieeexplore.ieee.org/document/11017335