The LAX Laboratory
Investigations of the interaction between radiation and matter as
well as the development of modern X-ray detectors for astrophysics
and medical researches require the availability of an X-ray beam with
wide ranges of variable energy, flux, transversal size and angular
Such an X-ray beam facility was installed at LAX
(Laboratorio per sperimentazioni con radiazione X),
jointly operated in Palermo by the DiFTeR and DEAF (Dipartimento di
Fisica e Tecnologie Relative e Dipartimento di Energetica ed
Applicazioni della Fisica) of the University of Palermo and IASF
(Istituto di Astrofisica Spaziale e Fisica cosmica) di
Palermo of INAF (National Institute of Astrophysics).
The X-ray beam has an operational energy range of 0.1 25
keV (extensible up to 60 keV) with a flux of 1010
1012 photons/sr . s. The beam, collimated on a
length of 10.5 m, has a diameter at full aperture of 200 mm with a
divergence of 1°.
A view of the LAX facility is reported below.
Some interesting applications of the LAX facility are:
For the intended applications the LAX X-ray beam facility with
good angular collimation fullfills the requirements and is much more
convenient, for example, of the Synchrotron radiation sources.
- Development, investigation and calibration of X-ray
detectors: energy resolution, spatial resolution, quantum
- Surface physics: material microstructure, reflectivity and
transmission of materials, photoemission from materials
- Absorption and transmission of matter: irradiation, radiation
As shown in the general layout of Fig. 2 the X-ray beam line
- the X-ray Generators;
- the Beam Collimation System;
- the Sample Chamber;
- the Detection Chamber.
The X-ray Generator Chamber operates at 10-9 mbar,
whereas the other parts operate at 10-6 mbar.
The beam line was developed and manufactured by RIAL Vacuum S.p.A.
(Parma, Italy) following the specifications of the DEAF and IASF.
The X-ray Generators
The X-radiation is produced by electrons accelerated in a vacuum
tube against an target as anode. X-ray lines can be obtained directly
from the primary target (then requiring a specific target material
for every line chosen) or by using the continuum derived from the
primary target to excite the fluorescence from secondary targets. The
high voltage can reach 60 kV.
Three X-ray Generator systems are available, covering different
energy ranges and allowing a flexible choice of the beam intensity.
The generators are easily interchangeable following the requirements
by the beam operation:
Flux value ranges from 1010 to 1012
photons/sr . s that means at 10 meters a flux of the order
of 105 photons/cm2 . s. A list of
available spectral lines is reported below.
- A Manson model Ultrasoft Source, covering the
energy range from 0.109 keV (Be-Ka)
to 1.254 keV (Mg-Ka).
- A Seyfert Air-insulated diffraction X-ray tube
type SN60 (max tube voltage 60 kV) covering the energy range from
1.0 keV up to 60 keV (W- Ka)
- An in house source electron gun induced variable
X-ray emission lines from several targets covering the energy range
from 0.109 keV (Be-Ka)
to 25.2 keV (Sn- Ka).
Table 1 : Targets and Energies of characteristic fluorescence
lines available at LAX
To minimize the Breemstrahulung continuum came from the primary
target and to select the lines originate from the primary or
secondary targets, absorption filters are also used. A list of
available absorption filters is given in the following table.
Table 2 : Thickness and purity of the absorption filters available
The Beam Collimation System
The maximum acceptable angular divergence is imposed by the
specific problem under consideration: minimum and maximum values
range from the arcsec to the degree of arc.
From the practical point of view, the angular divergence depends
upon the distance L between the X-ray generator and the Sample
Chamber and from the typical dimension D of the area illuminated,
which in turn determines the required power of the X-ray generator.
In the LAX beam, L=10.5 m and values of the order of 1°
obtainable for beam aperture of 200 mm diameter and of 1 for a
beam aperture of 2mm diameter.
The Sample Chamber
The Sample Chamber contains a table capable of translation along
the X, Y and Z axes and rotation around Y and Z. It hosts the sample
under analysis and/or monochromator/polarizes.
The Detection Chamber
The Detection Chamber hosts the X-ray
detectors; positioning is achieved by a micrometer table capable of
translation movements along the X and Y axes and rotation around Y.
The block layout of the X-ray beam line
is shown in Fig. 3.
X-ray Generator Chamber
The cylindrical chamber (Fig. 3
Pos. A Level 100) is made of stainless steel for UHV, with 4
CF 35 viewports, three CF 16, one CF 100 and one CF 63, Copper seals
The CF 100 closing flange has a CF 35
The two windows for X-ray transmission
are made of beryllium and mounted on CF 16.
The chamber is pumped by a
160 l/s diode ion pump provided with a CF 63 all-metal valve. The
power supply can be used to measure the vacuum. The operative vacuum
is better than 10-10 mbar.
Motion system are used for the electron
gun and the targets:
A 30 mm translation system mounted
on 2 CF 63 flanges.
It is used for the
translation of the electron gun, equipped with a bipolar feedthrough
CF 63, with inside connections for filaments and outside connection
for the HV connector (60 kV) compatible with the Seyfert
power supply cable.
Fig. 4||A 360° rotation 50 mm
translation system (see Fig. 4) is installed on a CF 100 flange to
support the various targets on a double helical octagonal pyramid.
The support is water cooled.|
First Lateral Beam Interceptor
The first lateral interceptor (Fig. 3 Pos. A Level 473)
of the X-ray beam is mounted after the CF 35 slide valve, with two linear
translators with a stroke of 30 mm moved by a stepping motor where
some slits are mounted to limit beam divergence.
X-ray Absorption Filter System
A disc filter system with 12 positions (Fig. 3 Pos. A Level
690) is mounted on a T chamber. Interchange of the filters is
performed by a routable manipulator controlled by a stepping motor.
Beam line: Pipes
Three stainless steel tubes of 200 mm of diameter (DN 200) are installed to
connect the X-ray source to the sample holder chamber. The overall
length of the pipe is quoted in the Fig. 3 Pos. C.
Second Lateral Beam Interceptor
This component (Fig. 3 Pos. C Level 8558) is mounted on a DN
200 cross piece with two linear X,Y manipulators, each with a 200 mm
stroke controlled by stepping motors, to collimate the X-ray beam.
flanges allow the mounting of vacuum gauge heads, and a by-pass for a
Varian 1000 l/s turbomolecular pump, coupled to an
Alcatel rotating vane pump (two stage, 65 m3/h)
DN 40 with zeolite filter, to maintain a vacuum in the pipes below to
Sample Holder Chamber
The Sample Holder Chamber is essentially made of:
Stainless steel chamber;
The chamber consists of a 6 way cross with a spherical body with
a CF 200; Four CF 35 flanges are added for possible services (vacuum
gauges, by-pass lines, etc.). The surface have been treated for UHV
- Five degree manipulators with three
micrometric linear X,Y,Z axes movements and two angular movements
around to Y axis and any axis in the X,Z plane. Z is the axis of the
- Introduction valve;
The valve is a
gate valve with CF 200 flange.
The Detection Chamber (Fig. 3 Pos. D Level 10169) for the
X-ray beam is made of stainless steel with UHV specifications. It
essentially consists of a horizontal cylinder, with an external
diameter of 1300 mm, thickness 10 mm and length 1300 mm with a curved
base. Both chamber and curved base are flanged. The curved base is
hinged to the chamber for easy opening. A seal system, realized with
two concentric Viton O-rings, can be differentially pumped. Four
supports are welded inside the chamber upon which the detection
system is fixed. Outside four supports are designed to allow the
levelling of the chamber.
The central cylinder is equipped with the following flanges: 10 flanges CF 200,
3 flanges CF 100, 4 flanges CF 35, 2 view ports CF 150. Two CF 200
flanges are mounted on the two covers.
Inside a three degree UHV micrometric table with two linear X,Y axes movements
and a one angular movement around the Y axis is placed and centred
along the beam line axis (Z axis). The dimension of the table is 200
x 200 mm and it can support a load up to 10 kg.
The chamber is He leak tested to a maximum leak rate of 1 x 10-9
atm cm3 s-1.
The pumping system consists of one Alcatel rotating vane pump
(two stage, 65 m3/h) DN 40 with zeolite filter, a 1000 l/s
pumping speed Varian turbomolecular pump and a
CTI-Cryogenics cryogenic pump with a nominal pumping
speed of 1500 l/s for air and 4000 l/s for water.
The operative pressure is below 10-6 mbar.
A combined Pirani-Penning gauge is used for vacuum measurement.
The adjustable supports for X-ray chamber and connection pipe are made of
painted iron with fine regulation screws (1/10 mm). They are used to
support the weight of the X-ray chamber, the ion pump and the
With different committments and tasks, the following IASF-Palermo people
are part of the LAX Team:
Filippo Celi (LAX Respons.) |
Salvo Giarrusso (Science Respons.) |
Giovanni La Rosa |
Giacomo Fazio |
Filippo.Celi at iasf-palermo.inaf.it
"Laboratory measurements of Air UV fluorescence Light Yield induced by X-ray
S. Giarrusso, O. Catalano, F. Celi, G. Fazio, G. La Rosa, T. Schillaci,
Proc. 26th ICRC, D. Kieda, M. Salamon, B. Dingus, (Eds.),
Vol.5, 449, 1999
"AIRWATCH: air induced fluorescence by radiation: laboratory experiments" ,
S. Giarrusso, O. Catalano, F. Celi,
G. Fazio, G. La Rosa, G. Richiusa, T. Schillaci, G. Bonanno,
R. Cosentino, R. Di Benedetto, S. Scuderi,
Proc. SPIE'98 Conf., 3445, 460-469, 1998
"The X-ray Facility at LAX in Palermo" ,
F. Celi, L. Dalla Bella, S. Ferrari, S. Re, G. Richiusa, L. Scarsi,
Vakuum in Fosrchung und Praxis,
1, 21-24, 1996
Last Modification: Monday, January 23 2012