A Classic Thesis Style - Johannes Gutenberg-Universität Mainz
A Classic Thesis Style - Johannes Gutenberg-Universität Mainz
A Classic Thesis Style - Johannes Gutenberg-Universität Mainz
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
36 experimental setup and data acquisition<br />
(a) (b)<br />
Figure 17: Measured efficiency for a set of different gas mixtures and pregap<br />
voltages as a function of the anode voltage. A saturation region<br />
or plateau is observed in all cases and a clear dependency of the<br />
plateau starting point on the other operating parameters can be<br />
seen. The effect of the pregap is shown in subfigure (b) where the<br />
pregap voltage is set to zero. Larger anode voltages are needed to<br />
achieve the same detection efficiency.<br />
and isobutan (C4H10): 7% at an anode voltage of 4.8 kV, and a pre-gap<br />
voltage of 7.5 kV. For their final installation in Kaos platform, the<br />
gas tubing system was renewed, optimizing gas flow and ensuring<br />
mixture uniformity within the chamber volume.<br />
2.4.5 Scintillator walls<br />
Two scintillator walls, labeled F and G, are used as timing and trigger<br />
detectors in the positive arm Kaos detector package. The F detector,<br />
located approximately in the focal plane of the spectrometer, consists<br />
of 30 plastic scintillators paddles (38 cm x 3.7 cm x 2 cm) of type Pilot<br />
F (modern equivalent: BC408) and 8 cm long lucite light guides. The<br />
paddles are tilted by 37 ◦ around the longitudinal axis in order to<br />
achieve an almost perpendicular flight path of the incoming particles<br />
into the 3.7 cm face. The total length covered by the wall is 1.89 m.<br />
The scintillators are read out in both ends by 2 in. Hamamatsu R1828<br />
phototubes to allow for light propagation compensation.A momentum<br />
resolution of about 4% is obtained with these 3.7 cm wide paddles.<br />
The G detector was added to the system permitting the implementation<br />
a rough angular selection trigger. It also consists of 30 scintillator<br />
paddles (47 cm x 7.5 cm x 2 cm), with a purely flat geometry spanning<br />
a length of 2.2 m and read out by the same type of phototubes. Plastic<br />
scintillator material is BC408. This fast scintillators (2.1 ns decay<br />
constant) are very suitable for time of flight measurements and still<br />
feature a large absorption length of 380 cm.