[HN Gopher] LHC's New Chip Tackles Radiation Challenges
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       LHC's New Chip Tackles Radiation Challenges
        
       Author : rbanffy
       Score  : 22 points
       Date   : 2025-08-10 14:33 UTC (8 hours ago)
        
 (HTM) web link (spectrum.ieee.org)
 (TXT) w3m dump (spectrum.ieee.org)
        
       | magicalhippo wrote:
       | 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
        
         | hinkley wrote:
         | I'm shocked that's a high enough sampling rate.
        
           | brcmthrowaway wrote:
           | Maybe they use aliasing?
        
           | tux3 wrote:
           | 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 wrote:
             | So the clock skew is high resolution but the clock rate is
             | low. Makes sense.
        
         | SiempreViernes wrote:
         | 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 wrote:
           | 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/cb39822f5ead85e84d7a1221bcd
           | 68fa...
        
       | thrance wrote:
       | 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.
        
         | pstuart wrote:
         | They really pulled a boner there.
        
         | HPsquared wrote:
         | 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!
        
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