1Yu. Guz

HCAL 137Cs calibration run 05/07/2011

20/07/2011

2Yu. Guz

HCAL 137Cs calibration 05/07/2011

Deviation of 137Cs currents from nominal is shown. The nominal calibration was last time restored by modifying the HV according to the result of the previous 137Cs calibration, 09/05/2011 (57 days, integrated luminosity 339 pb-1). The variation of -39%...+31% is seen in 137Cs current. A systematical response reduction in the central region, as expected. Caused not only by PMTs but partially by plastic/fibers ageing (see next slides). The HV change necessary for the correction is also shown. The HV PHYSICS and DEFAULT recipes were updated on 07-Jul. The previous recipe is kept as PHYS_MAY2011. The HV change was rather significant in the HCAL central cells, and led to a noticeable increase of the L0hadron rate compared to the end of June.

20/07/2011

3Yu. Guz

LED: 09-May (91054) and 05-Jul (94664)Source: 09-May and 05-JulA reasonable correlation between Cs and LED variations.

20/07/2011

137Cs vs LED

A good correspondence between expected gain change (@oldHV) / (@newHV) and ratio of LED amplitudes taken at old HV (run 94664) and at new HV (run 95215): 2 days between these measurements.

Verification of the new HV recipe.Source vs LED variation 05-July / 09-May

4Yu. Guz

reminder: HCAL calibration 09/05/2011

Comparison to the 16-Feb-2011 calibration when nominal gains were set (82 days, integrated luminosity 95 pb-1). The gain variation -41%...+22% seen. A systematical gain reduction in the central region, as expected. The HV change necessary for the correction is also shown (-46V…+106V). This is significantly more than 29-Mar (only 9 pb-1, previous slide). The HV PHYSICS recipe was updated on 12-May. The old recipe is kept as PHYS_MAR2011.

22/06/2011

HV change necessary

for the correctio

n

Similar modification done on 09-

May

5Yu. Guz

(search for) radiation-induced effects

20/07/2011

6Yu. Guz

The 104 integrator boards are installed on the HCAL rear surface, in the PMT compartment, at 1—4.5 m away from the beam, where the dose is moderate.No significant drift of the integrator sensitivities, as expected (max change ~0.4%).

20/07/2011

Integrator sensitivity change 2011/2009

7Yu. Guz

This could be seen in the comparison of 137Cs calibration results before and after certain data taking period (in 137Cs calibration, responses of every single scintillator tile are determined).

20/07/2011

Radiation damage of tiles and fibers

beam

PMT

spacers

WLSfibers

lightguidemaste

r plate

scintillators row 0row 1row 2

row 3

row 4

row 5

The hadronic shower maximum lays ~ within the tile row 0; the dose in the row 5 is much less. Radiation damage of scintillator tiles and fibers can therefore manifest itself as a decrease of relative response of upstream rows (0, 1) with respect to row 5.

8Yu. Guz22/06/2011

a % decrease in the central area in rows 0, 1 and maybe 2. Only a small effect (if present at all). To be followed in further source runs: ~300 pb-1 between 05-Jul and 09-May!

Reminder: 09-May vs 29-Mar (86 pb-1)

Radiation damage of tiles and fibers

9Yu. Guz20/07/2011

Now the effect is better visible (note also different Z scale): ~-3…-6% in the central cells at row 0

05-Jul vs 29-Mar (424 pb-1)

Radiation damage of tiles and fibers

10Yu. Guz

The LED data taken right after the HV correction are used. It is assumed that the Cs currents at these moments exactly correspond to the nominal. Visible discrepancy between Cs and LED is seen in the central cells: consequence of plastic ageing.

20/07/2011

LED/Cs variation July / May