**Mar345 Image Plate Detector**

2/21/2005

A)  Introduction

> The Mar345 Image Plate is a circular detector^1^ with a maximum
> diameter of 345mm. The actual measurement diameter can be selected to
> be either180, 240, 300 or 345mm. There are two selectable pixel sizes,
> 150um X 150um or 100um X 100um. The corresponding read out time is
> different for different choice of measurement diameter and pixel size.
> Sensitivity of the detector is 1 X-ray photon per ADC unit at 8 keV.
>
> The detector stores an X-ray image as a collection of F-centers in a
> phosphor screen. The locations of the received X-ray photons are
> represented by the spatial distribution of the F-centers. The X-ray
> intensity is calculated in term of the intensity of the fluorescence
> induced by a He-Ne laser during the read out process.
>
> The detector is controlled by software^2,3^, mar345, supplied by the
> vendor (Mar Research). The control computer runs under the RedHat
> implementation of Linux. It contains two Ethernet cards, one of them
> talks to the intranet that the control computer is attached to and the
> other one communicates with the detector through a red Cat5 cable. The
> Ethernet card that is responsible for intranet connection can use
> DHCP, that means its address is dynamically assigned during boot up,
> however, the other card should have a fixed address of 192.0.2.2. The
> Ethernet address for the detector will always be 192.0.2.1.
>
> The net weight of the detector alone is about 53kg (\~120lbs), so care
> should be taken when handling the detector. Delicate components such
> as the Be window in front of the detector can easily be damaged on
> impact. So it is recommended to have at least two persons to move the
> detector.
>
> For more specifications on the detector please go to the Mar website:
>
> [http://www.marresearch.com](http://www.marresearch.com/)
>
> Section B of this document is the general operation principle of an
> Image Plate (IP). We list out in Section C all the components for the
> detector system that you should get from the detector pool. Check the
> list during check out time and please return the system in its
> entirety after the experiment. Section D and E will guide you through
> the system set up process step by step. Finally in section F we have
> listed some reference material for the detector.

B)  Principle of operation

> The IP utilizes the charge capturing capability of F centers. An F
> center is one kind of crystal defect in ionic crystals^4^, for example
> NaCl. NaCl crystal has a face-centered cubic (FCC) structure, each ion
> has 6 nearest neighbors. If a point defect happens to the crystal and
> a Cl^-^ is missing from its proper location, the vacant site will lack
> negative charge because a perfect ionic crystal is macroscopically
> neutral. The neighboring 6 Na^+^ ions will essentially form a trap (an
> F center) for electrons. Pure alkali halide crystals are transparent
> throughout the visible region of the EM spectrum, but heating NaCl
> crystal in the presence of sodium vapor makes the crystal appear
> yellowish due to the formation of F centers.
>
> The IP of Mar345 is a CR standard ST-V plate manufactured by Fuji
> Photo Film Company Limited. In order to explain the basic physics of
> an IP we will use a similar system, Europium-activated BaFX:Eu^2+^ (X
> = Cl, Br, I) crystal^5-8^. The crystal contain two types of F center,
> F(F^-^) and F(X^-^). The corresponding IP is usually made of flexible
> plastic material intermixed with small size phosphor crystals (\~5 m
> in size) to a thickness of about 150 m. The piece of plastic is then
> laid on a thicker backing material for support.
>
> The mechanism of X-ray detection by BaFX:Eu^2+^ crystal has been
> proposed by Kenji Takahashi et al^9^. When an X-ray photon is absorbed
> by an IP, the process will cause electron transfer from the valence
> band to the conduction band of the crystal. Some of those events will
> correspond to the ionization of Eu^2+^ to Eu^3+^ ion. The transferred
> electron may then captured by one of the F centers and temporarily
> stored there. The captured electron can subsequently be released by a
> process called photon stimulated luminescence (PSL), in which the
> crystal is locally irradiated with He-Ne laser ( = 632.8nm). The
> purpose of the laser photons is to provide activation energy for the
> trapped electron to get away from the F center. The electron then
> recombines with a Eu^3+^ ion and gives out a characteristic radiation,
> with 390nm, that corresponds to an electron transition from the 5d to
> the 4f orbital of the Eu^2+^ ion. The visible photon emitted is then
> analyzed by a photomultiplier tube with adjustable gain. The intensity
> of the visible light signal given out is linearly proportional to the
> intensity of the absorbed X-ray over a wide dynamic range.
>
> Mar Research uses a proprietary read out mechanism for their Mar345 IP
> system. Before an exposure, the IP is locked down by an internal
> electromechanical latch.
>
> The IP is then exposed to X-ray signal. The information on the IP is
> then read out using a mechanism that is similar to that of a computer
> hard drive. The reading head contains a stimulating laser, a collector
> cup and a photomultiplier. The reading head drives down from the edge
> to the center of the plate while the image plate spins according to a
> pre-determined speed profile. The stored information is then read out
> pixel by pixel by the reading head. Mar calls this process a spiral
> scan. The driving motion of both the read head and the plate ensures a
> constant pixel read out time over a large area of the plate. The
> maximum rotation speed of the plate is 3800rpm. The pixel size is
> determined by the beam size of the stimulating laser for this
> particular detector.
>
> After relevant data have been read the whole IP can be erased, and
> therefore returned to its ground state, by illuminating the plate with
> the three built in halogen lamps. The erase process is the same as
> doing a read scan but no data are collected. It is always a good idea
> to do a plate erase before taking data.

C)  Detector and Accessories

> The detector contains the following items from the detector pool:
>
> Mar345a)

  -------------------------- --------------------------------------------
  DP00037                    Mar 345 (Image plate)

  DP00038                    Computer (BSI)(EPIC)(Linux)

  DP00099                    Front cover for Mar345a

  DP00106                    Red pneumatic cart for Mar345a

  DP00118                    Red Cat5 cable for Mar345a
  -------------------------- --------------------------------------------

> Mar345b)

  -------------------------- --------------------------------------------
  DP00100                    Mar 345 (Image plate)

  DP00028                    BSI monitor and keyboard assembly

  DP00069                    Computer (Mar Image Plate software)(Linux)

  DP00107                    Red pneumatic cart for Mar345b

  DP00098                    Front cover for Mar345b

  DP00116                    Red Cat5 cable for Mar345b

  DP00122                    Mouse for Mar345b
  -------------------------- --------------------------------------------

D)  Physical Connection

    1.  Secure the detector in the proper location in the experimental
        setup.

    2.  Make sure both the detector and the control computer are turned
        off.

    3.  Make an Ethernet connection between the detector and control
        computer as in Figure 1.

> Connection from control computer to intranet.
>
> ![](media/image1.jpeg){width="2.379861111111111in"
> height="2.154166666666667in"}
> ![](media/image2.jpeg){width="2.5006944444444446in"
> height="2.173611111111111in"}

Ethernet connection from detector to control computer.

> Figure 1. The detector is on the left hand side and the control
> computer is on the
>
> right. Connect a Cat5 cable from the detector's RJ45 connector to the
> Ethernet connector 1 on the back of the computer. Connect Ethernet 0
> of the computer to the intranet.

E)  Software Start Up

    1.  Switch on the detector.

    2.  Switch on the control computer.

    3.  When the computer operating system, in this case RedHat Linux,
        is mounting all its peripherals there should be status lines on
        the screen saying that

> "bringing up Ethernet 0 ............................ Ok "
>
> "bringing up Ethernet 1 ............................ Ok ".
>
> That means both of the Ethernet cards on the host computer are mounted
> successfully.

4.  Then the window manager will bring up a log in screen. Root (super
    user) and user password will be provided, however, do not log into
    the computer as root unless absolutely necessary and you completely
    know what is happening. Normally by logging in as user, you should
    be able to get all the processing capabilities that are need during
    an experiment. If logged in as root (super user), permanent damage
    to computer setting can be made.

5.  After logging in as a user, bring up a terminal and use the ping
    function to check the communication between the control computer and
    the detector. At the command prompt type "ping 192.0.2.1". Then you
    should get the following message,

> PING 192.0.2.1: 56 data bytes
>
> 64 bytes from 192.0.2.1: icmp_seq=0 ttl=255 time=1ms

....

....

> If you received the above message the communication between the
> computer and the detector is working.

6.  After the command prompt type "mar345". The mar345 detector will
    warm up and a large clicking noise will be heard when finished, then
    main screen will appear. The noise is due to the activation of the
    electromechanical latch that holds the IP in position.

> ![](media/image3.jpeg){width="3.004861111111111in"
> height="2.404166666666667in"}
>
> Figure 2. Main screen of the Mar345 control software. The larger white
> display area is for the display of image after scanning. The narrow
> tool bar at the right hand side consists of three sections: the menu
> bar, the system status information section and the system control
> section.

7.  The different functions that are available on the menu bar and
    system control section are described in detail in the mar345 Program
    Manual provided by Mar Research.

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F)  References

    1.  MarResearch, Mar345 : Technical Specifications

    2.  Claudio Klein, The mar345 Software Guide **Version 1.2**, (2001)

    3.  Claudio Klein, The mar345 Program Manual **Version 2.0**, (2000)

    4.  Charles Kittel, Introduction to Solid State Physics **7^th^
        Edition**, 499 (1996)

    5.  Yoshiyuki Amemiya, J. Synchrotron Rad. **2**, 13 (1995)

    6.  Junji Miyahara, Kenji Takahashi, Yoshiyuki Amemiya, Nobui
        Kamiya, Yoshinori Satow, Nucl. Instr. and Meth. **A246**, 572
        (1986)

    7.  M. Yuste, L. Taurel, M. Rahmani, D. Lemoyne, J. Phys. Chem.
        Solids **37**, 961 (1976)

    8.  K. Takahashi, J. Miyahara, Y. Shibahara, J. Electrochem. Soc.
        **132**, 1493 (1985)

    9.  Kenji Takahashi, Katsuhiro Kohda, Junji Miyahara, Yoshihiko
        kanemitsu, Koji Amitani, Shigeo Shionoya , J. Luminescence
        **31&32**, 266 (1984)