sPHENIX HCal discussion

[Edward Kistenev <kistenev AT bnl.gov>]

Here is my problem with that jumpy picture.

When readout was triggered by internal trigger (combination of 8 SiPM’s signals digitized to 9 bits at 60 mhz) events walked 5 clocks with respect to the start of the information window (23 clocks if I remember right). It never was random, the data would move one clock event-to-event and then jump back.  It is not clear if effect in the movie is the same or real random but I used my data trying to estimate HCal timing resolution for muons and could not really prove to myself if ~2ns which I’ve seen in the data are intrinsic or connected to uncertainties with phase latching.

I am planning to use selftrigger to calibrate HCal first in the high bay then at FNAL  and will feel safer with this plan if that kind of systematics was at least explained. 

Edward

Edward Kistenev, PhD

PHENIX Physicist

On Nov 23, 2015, at 11:16 AM, Mickey Chiu <chiu AT bnl.gov> wrote:

Hi Edward,

The trigger is clocked in on the 10 MHz clock, so it has a resolution of ~100 ns, i.e., roughly your 5 16 ns clock ticks.  Since the cosmic trigger is totally asynchronous, it will come in with a random and flat distribution in time, and thus you’ll see the “walk” you mentioned.  It’s not really a “walk”.  You’re just seeing the phase of the cosmic signal relative to the edges of the 10 MHz clock.  The triggering on a 10 MHz cycle is obviously designed to sync with RHIC.

John isn’t using the self-triggering for this.  He’s externally triggered on a 2-paddle coincidence.

Mickey

On Nov 23, 2015, at 5:22 AM, Edward Kistenev <kistenev AT bnl.gov> wrote:

Your picture is jumping back and forth for 5 16 ns clocks what makes me wander if you were running with self trigger (remember this funny trigger walk which Chi promised to explain). I never checked if walk persists in the data triggered by  external scintillators. If it is - may someone explain how and why this beating is generated.

Edward

Edward Kistenev, PhD

PHENIX Physicist

On Nov 23, 2015, at 2:07 AM, John Haggerty <haggerty AT bnl.gov> wrote:

Abhisek, Megan, and I set up a stack of five inner hcal tiles acquired
by Edouard from Uniplast, wrapped by Mike Lenz, with SiPM holders for
Sean's SiPM's from Richie and preamps from Steve and Sal on Friday (you
get the idea; it takes a village).  There's serious stuff to do, but I
thought this animated gif of cosmic rays was fun:

https://www.phenix.bnl.gov/WWW/p/draft/haggerty/sphenix/cosmic_1191.gif

It shows waveforms from the five tiles on the left and the discriminated
trigger scintillators on the right.  (The animated gif of 100 events
should play in your browser forever because it loops.)  The raw data are
in rcf at

/direct/phenix+user04/sphenix/bnl/buffer/rc-01191-0.prdf

--
John Haggerty
email: haggerty AT bnl.gov
cell: 631 741 3358
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