1

Trend ground array

1. General considerations2. Study on the prototype detector3. Inclined ground array simulation4. Making work plan in 2014

2

1. General considerations

1.1 The prototype detector is similar to the one used in the Tibet ASg experiment. The scintillators, PMTs and detector boxes will be bought or manufactured together with the upgrade project of the Tibet ASg experiment.

1.2 Some independent issues, such as lead, HV power supply and the shielding system should be bought, designed and/or manufactured independently.

1.3 Laboratory test with the optical system is to be performed with the prototype detector we have already had---to test the PMT signals.

2.1 Test of the scintillators provided by different companies A comparison measurement between Chinese KD scintillator and international EJ scintillator has been made: The KD scintillator’s light yield is about 66% of the EJ one.

2. Study on the prototype detector

PMT2

XP2020 Dark box

5cmX5cmX5cm

PMT1 ET9814

Scintillator

Scintillator

(334.7*3/5)/303.4=~66%

2.2 Investigation of the reflective materials Different reflective materials, for instance, Teflon, Tyvek 1082D and black paper were selected to test their influence on the light collection. The experimental result shows that the reflectivity of the wrapping material plays a remarkable role in the light collection.

5

Before sanded---transparent

After sanded---opacity

Holding the scintillator to move irregularly on the surface of fine sandpaper No.800 and then No.600.

600# 800#

2.3 Study on the dependence of the light collection on the scintillator’s surface roughness Two EJ-200 plastic scintillators were used. One of them is with four clear edges and two polished faces. Another one is with four clear edges, one polished face and one sanded face. The inner surface of the detector box, the underside and four edges of the scintillator are covered with Tyvek paper. Comparison measurement result shows that the sanded face one gives an increase of collected light by ~20%.

Detector box design

6

7

Prototype detector design

• Plastic scintillator– Type: EJ-200– Size:707mm*707mm*20mm– Surface: four clear edges, one polished

face and one sanded face. • Reflective material:

– Tyvek 1082D • PMT - See Zhaoyang’s report.

Waveform from oscilloscope

采样②

采样③

Sample①

Sample ③

Sample②

PMT： Gain~2.7*10^6

Average in 128 times

Single particle signal

Amplitude ： -98mV

Width ： ~75ns

Fall time ： 43.9ns

Rise time ： 8.6ns

1. SPP

2. Time resolution

2.4 Performance of the prototype detector and MC simulation

(1)There are ~80 photons per single particle. Its time resolution is ~1.1ns.

(2)The experimental results are in good agreement with the simulation.

10

Light yield uniformity of the detector is carried out by changing the position of the trigger detector. Above experimental data plot is obtained along the diagonal line of the detector shown in the right figure.

(3) The light yield non-uniformity of this detector is not greater than 35%

Event Rate/day:The event number of observation at different zenith angle for different detector tilted angle.

3. Inclined ground array simulation

12

4. Making work plan in 2014

1. Study on the prototype detector, including:(1) the design and manufacture of the detector box

(some modifications)(2) the methods to fix the reflective materials used in the inner surface of the detector box(under the way)(3) Selection and test of the magnetic shielding material used to wrap the PMT (under the way)(4) Investigation on the detector support and water proof for the inclined measurement(under consideration)

13

2. Design and test of the HV power supply system.3. Study on the PMT signals with the optical system via the prototype detector we have already had.4. Manufacturing 21 sets of detectors together with the upgrade project of the Tibet ASg experiment.

14

Discussion results

• S1: • S2: • S3: • S4: