X-ray fluorescence (XRF) set-up with a low power X-ray tube Sheenu Gupta a , Kanan Deep a , Lalita Jain b , M.A. Ansari b , Vijay Kumar Mittal a , Raj Mittal a,n a Nuclear Science Laboratories, Physics Department, Punjabi University, Patiala 147 002, India b Laser Electronic Support Section, Raja Ramanna Centre for Advanced Technology (RRCAT), Indore, India article info Article history: Received 25 February 2010 Received in revised form 4 May 2010 Accepted 4 May 2010 Keywords: XRF set-up Low power X-ray tube 3D arrangement and minimum detection limit abstract The X-ray fluorescence set-up with a 100 W X-ray tube comprises a computer controlled system developed for remote operation and monitoring of tube and an adjustable stable 3D arrangement to procure variable excitation energies with low scattered background. The system was tested at different filament currents/anode voltages. The MDL of the set-up at 0.05–1.00 mA/4–12 kV is found (1–100) ppm for K and L excitations and  (200–700) ppm for M excitations of elements and improves with filament current and anode voltage. Moreover, L measurements for Sm and Eu at five K X-ray energies of elements(Z ¼29–40) and analytical determination in some synthetic samples were undertaken. & 2010 Elsevier Ltd. All rights reserved. 1. Introduction The study of X-ray fluorescence (XRF), emission of X-rays from an element excited by external photons, can be done with widely used photon sources such as radioactive sources, synchrotron radiation and X-ray tubes. With radioactive sources, the limita- tions (Van Grieken and Markowicz, 2002) arise due to limited photon energy range and intensity of photons emitted from the sources. But X-ray tube and synchrotron photon sources take care of these limitations. A synchrotron photon source is a multi-user facility and involves huge expenses, infrastructure and man- power. So far, for laboratory experiment, X-ray tube photon source is an appropriate source to have high intensity of photons. Such systems are existing worldwide in different XRF laboratories (Standzenieks et al., 1978; Reeves et al., 1995; Ali et al., 1998; Ryon, 2003; Ida and Kawai, 2005). A similar system has been developed in our laboratory with a 100 W X-ray tube. The developed system and its use for XRF studies and analytical measurements are being detailed in the following sections. 2. X-ray tube photon source The X-ray tube photon source comprises a low power Neptune X-ray tube of Oxford Instruments, USA with Coolidge based Rh target as anode and 2 mA/50 kV maximum filament current/ anode voltage. The tube was imported with additional infra- structure; a 100 W regulated high voltage direct current (HVDC) power supply and a water cooling system. The HVDC power supply provides two analog inputs to the tube, high voltage for anode and current for filament. The cooling system provides requisite cooling for 100 W of dissipated power and maintains the temperature of the tube within the limit. The supply also comprises a safety interlock system. The continuous exposure to radiation is harmful for human health, hence it is mandatory to operate the tube remotely. To operate the tube remotely, a computer controlled system for the tube power supply was installed in Laser Electronic Support Section, Raja Ramanna Center for Advanced Technology, Indore, India (Jain et al., 2008). The control system consists of two parts: (a) personal computer (PC) that provides graphical user interface (GUI) to set voltage to anode and current to filament and to display the read back signals and (b) micro-controller unit (MCU) that is interfaced with subsystems of X-ray source. The PC is serially connected to MCU through RS-232 link. The interlocks were also hardwired in micro- controller that become active in case of any fault and switch off the X-ray source immediately. The controller controls and monitors the following signals of X-ray power supply:  High voltage DC power supply: It provides control voltage 0–10 V corresponding to HVDC (0–50 kV) and monitors the read back in the range of 0–50.  Filament current: It provides control voltage 0–10 V corresponding to the filament current (0–2 mA) and monitors the same.  Moreover, it provides the interlock status like coolant flow, coolant level, water temperature and HVDC interlock. For safe operation of the system and to get shielded from the tube radiation, the X-ray source was mounted in a cabin of dimensions 60 cm  60 cm  60 cm made from angular iron, ARTICLE IN PRESS Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/apradiso Applied Radiation and Isotopes 0969-8043/$ - see front matter & 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.apradiso.2010.05.001 n Corresponding author. Tel.: + 91 9417284302; fax: + 91 175 2283073. E-mail address: rmsingla@yahoo.com (R. Mittal). Applied Radiation and Isotopes 68 (2010) 1922–1927