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\begin{document}

\title{A new active base of photomultiplier R4125 designed for the PbWO$_4$ calorimeter}


\author{\IEEEauthorblockN{1\textsuperscript{st} Fernando Barbosa}
\IEEEauthorblockA{\textit{Thomas Jefferson National Accelerator Facility} \\
Newport News, USA  \\
barbosa@jlab.org}
\and
\IEEEauthorblockN{2\textsuperscript{nd} Vladimir Berdnikov}
\IEEEauthorblockA{\textit{Thomas Jefferson National Accelerator Facility} \\
Newport News, USA  \\
berdnik@jlab.org}
\and
\IEEEauthorblockN{2\textsuperscript{nd} Vladimir Popov}
\IEEEauthorblockA{\textit{Thomas Jefferson National Accelerator Facility} \\
Newport News, USA  \\
berdnik@jlab.org}
\and
\IEEEauthorblockN{2\textsuperscript{nd} Alexander Somov}
\IEEEauthorblockA{\textit{Thomas Jefferson National Accelerator Facility} \\
Newport News, USA  \\
somov@jlab.org}
}

\maketitle

\begin{abstract}
This paper presents the design, performance, and results of the radiation tests of an active base for  Hamamatsu R4125 photomultiplier tube. 
The active base was designed at Jefferson Lab and comprises of a high voltage divider and an on-board amplifier. The photomultiplier with the 
active base is used to detect light from lead tungstate scintillating crystals of the forward electromagnetic calorimeter of the GlueX detector. 
The active base amplifier allows to operate the tube at lower high voltage and thus to limit the photomultiplier 
anode current to a few micro ampereres at the maximum counter rate of 1 MHz counter, while retaining the dynamic range of output signals.
The performance of calorimeter modules instrumented with the active base was studied using detector prototypes positioned into the beam of photons.
The key performance parameters such as the linearity, high-rate capability, and the energy resolution verified that the active base design 
meets the detector specifications. The resistance of the active base components to radiation was studied using Caesium-137 source. Some damages 
observed required to make  modifications to the original base design. 
     

\end{abstract}

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\section{Introduction}

\subsection{Test}

\begin{figure}[htbp]
\centerline{\includegraphics[width=1.0\linewidth]{divider.jpg}}
\caption{Active base for Hamamatsu R4125 photomultiplier tube.}
\label{fig}
\end{figure}

\begin{figure}[htbp]
\centerline{\includegraphics[width=1.0\linewidth]{rate.png}}
\caption{Signal amplitude induced by a laser pulser as function of the rate.}
\label{fig}
\end{figure}

\begin{figure}[htbp]
\centerline{\includegraphics[width=1.0\linewidth]{linearity.png}}
\caption{Signal pulse amplitude obtained from the calorimeter module as a function of the photon beam energy. The amplitude is given in units of flash ADC counts.}
\label{fig}
\end{figure}


%\begin{figure}[htbp]
%\centerline{\includegraphics[angle=-90,width=0.5\linewidth]{irrad_setup.jpg}}
%\caption{Degradation of an active base amplitude induced by an LED as a fanction of the accumulated dose.}
%\label{fig}
%\end{figure}

\begin{figure*}[htb]
\centering
$\vcenter{\hbox{\includegraphics[angle=-90,width=0.2\linewidth]{irrad_setup.jpg}}}$
\hspace{0.1in}
$\vcenter{\hbox{\includegraphics[width=0.3\linewidth]{pulse_before_damage1.png}}}$
\hspace{0.1in}
$\vcenter{\hbox{\includegraphics[width=0.3\linewidth]{pulse_after_damage1.png}}}$
\caption{Signal pulse induced by an LED before irradiation (left) and after the failure of the power regulator at a dose of 20 kRad (right).}
\label{fig}
\end{figure*}


\begin{figure}[htbp]
\centerline{\includegraphics[width=1.0\linewidth]{amp_vs_dose.png}}
\caption{Degradation of an active base amplitude induced by an LED as a fanction of the accumulated dose.}
\label{fig}
\end{figure}



\section*{Acknowledgment}
Work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177.

\begin{thebibliography}{00}
\bibitem{b1}
T.~Horn, \textit{et al.}, ``Scintillating crystals for the Neutral Particle Spectrometer in Hall C at JLab,''Nucl. Instrum. Meth. A \textbf{956}, 
163375 (2020).
\bibitem{b2}
A.~Somov, ``Jlab Eta Factory Experiment in Hall D,'' PoS \textbf{CD2021}, 029 (2024).
\bibitem{b3}
A.~Asaturyan, \textit{et al.}, ``Electromagnetic calorimeters based on scintillating lead tungstate crystals for experiments at Jefferson Lab,''
Nucl. Instrum. Meth. A \textbf{1013}, 165683 (2021).
\end{thebibliography}

\end{document}

