summary day shift 7-28 C

From: zhangchi (zhangchi@general.lns.mit.edu)
Date: Mon Jul 29 2002 - 00:15:56 EDT


Hi all,

I included Tancredi's summary for 8:00-16:00 shift as my work is a direct
continuation of his.

Although beam kept tripping in the first few hours and ROC still hang from
time to time, we managed to collect some data.

RUN 904-920 are with the trigger Tancredi left with. With these runs
resonable statistics are achieved expect for paddle 13 in coincidence with
paddle 5. By reasonable statistics, we mean the elastic proton peak rises
high enough above the noice such that a gaussian fit can be applied to it.
Number of events within this peak obtained by integration. Counts of
electron left/proton right and electron right/proton left can now be
compared quatitively. Please see `tdc_diff_lt.C'

We then ran with trigger with paddles 11 12 13 14, and any one of 2,3,4,5.
proton counts are obtained. Unfortunately, we did not have time to run
with paddle 4 5 in the trigger. The runs with 11 and 12th paddles are
rather short too.

No one is coming for the mid-night shift. Gas flow is shut down,
highvoltages are zeroed.

Doug and Chi

On Sun, 28 Jul 2002, Tancredi Botto wrote:

>
> In the first two plots attached I show
>
> proton (mean)time - electron (mean)time = proton TOF
>
> the first peak corresponds to background events (that are higher
> in number on the BL side, facing the ring) while the small peak
> at about 300 channels away (15 ns) is due to elastic protons.
>
> In the second plot I show the coplanarity (correlated TDC differences).
>
> Our trigger was paddles 12,13 AND 2,3,4,5, symmetrically for the L and R
> sector. Each row corresponds to a "proton paddle", respectively 12L, 13L,
> 12R, 13R and each column to an electron paddle. DAta was taken without the
> start counter (physically removed). It shows that there is a rather
> symmetric distribution of protons in both the left and right sectors.
> However, this is not perfect. As you can see, protons are missing from
> paddle 12L (in coinc with 2R), while this is not true for 12R&2L
>
> One possible explanation could be alignement. Presently there are no hard
> stops for the detector subframes, and one can expect their positioning is
> good to within (or up to) an inch to the beam line and releatively to each
> other. At a 3 mt distance from the target this could correspond to up to a
> 0.6 deg difference in the hadron angle, which in turn is a 20 % difference
> in cross section. Things may not be so tight as we have an extended
> target.
>
> However, in future runs this evening we will "enlarge" the number of
> hadron paddles in the trigger and continue analysis. The missing protons
> should show up in the relevant neighbours. THis study however is not
> strictly required to move on to the next part of the commissioning
> program.
>
>
> In the third plot I show raw physics trigger rates (for the trigger
> configuration above) with an empty and a 1 sccm target. There are clearly
> non linear, which is not surprising. Note how they correlate with the
> inverse lifetime. Injection current today was up to 120 mA, but the beam
> has a very short lifetime in the 80 -120 mA range. The above empty target
> rate at 110 Hz was 1 KHz (!).
>
> No effort was put in optimizing the background, as we stayed without beam
> for quite some part of our shift (frequent ring RF trips).
>
> Also, It was not possible to move the start counter back to the beam left
> side as a flange in the scattering chamber has been modified such that
> there is no room for the start counter anymore. However, recent data and
> the analysis at page 47 of the logbook shows clearly that the retime issue
> is dead. Going back at this point would mean opening the vacuum on beam
> left.
>
> regards
> -- tancredi
>
> ________________________________________________________________________________
> Tancredi Botto, phone: +1-617-253-9204 fax: +1-617-253-9599
> research scientist MIT/Bates, 21 Manning Av Middleton MA, 01949
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>



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