Møller polarimeter reconstruction in Hall A Jefferson Lab
The Møller polarimeter reconstruction for measuring of the electron beam polarization with energies up to 11 GeV has been performed in Hall A Thomas Jefferson Laboratory (United States). This paper describes the elements of the Møller polarimeter and accelerator beamline that have been changed. The...
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nasplib_isofts_kiev_ua-123456789-1118012025-02-09T21:54:50Z Møller polarimeter reconstruction in Hall A Jefferson Lab Модернізація мьоллерівського поляриметра залу А лабораторії ім. Т. Джефферсона Модернизация мёллеровского поляриметра зала А лаборатории им. Т. Джефферсона Pomatsalyuk, R.I. Vereshchaka, V.V. Glamazdin, A.V. Элементы ускорителей The Møller polarimeter reconstruction for measuring of the electron beam polarization with energies up to 11 GeV has been performed in Hall A Thomas Jefferson Laboratory (United States). This paper describes the elements of the Møller polarimeter and accelerator beamline that have been changed. The structure and characteristics of the modified data acquisition system of the polarimeter are shown. An analysis of components of systematic error of beam polarization measurement for two types of used targets is presented. В лаборатории им. Т. Джефферсона (США) проведена реконструкция мёллеровского поляриметра зала А для обеспечения измерений поляризации пучка электронов с энергией до 11 ГэВ. В работе описаны элементы мёллеровского поляриметра и электронопровода ускорителя, которые были изменены. Приведены структура и характеристики модифицированной системы сбора данных поляриметра. Проведён анализ величины систематической ошибки измерения поляризации пучка для двух типов используемых мишеней. У лабораторії ім. Т. Джефферсона (США) проведено реконструкцію мьоллерівського поляриметра залу А для забезпечення вимірювань поляризації пучка електронів з енергією до 11 ГеВ. У роботі описані елементи мьоллерівського поляриметра та електронопровода прискорювача, які були змінені. Наведено структуру та характеристики модифікованої системи збору даних поляриметра. Проведено аналіз величини систематичної помилки вимірювання поляризації пучка для двох типів мішеней, що використовувались. 2013 Article Møller polarimeter reconstruction in Hall A Jefferson Lab / R.I. Pomatsalyuk, V.V. Vereshchaka, A.V. Glamazdin // Вопросы атомной науки и техники. — 2013. — № 6. — С. 48-52. — Бібліогр.: 6 назв. — англ. 1562-6016 PACS: 29.25.Pj; 29.27.Hj; 29.85.Ca https://nasplib.isofts.kiev.ua/handle/123456789/111801 en Вопросы атомной науки и техники application/pdf Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Элементы ускорителей Элементы ускорителей |
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Элементы ускорителей Элементы ускорителей Pomatsalyuk, R.I. Vereshchaka, V.V. Glamazdin, A.V. Møller polarimeter reconstruction in Hall A Jefferson Lab Вопросы атомной науки и техники |
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The Møller polarimeter reconstruction for measuring of the electron beam polarization with energies up to 11 GeV has been performed in Hall A Thomas Jefferson Laboratory (United States). This paper describes the elements of the Møller polarimeter and accelerator beamline that have been changed. The structure and characteristics of the modified data acquisition system of the polarimeter are shown. An analysis of components of systematic error of beam polarization measurement for two types of used targets is presented. |
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Article |
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Pomatsalyuk, R.I. Vereshchaka, V.V. Glamazdin, A.V. |
| author_facet |
Pomatsalyuk, R.I. Vereshchaka, V.V. Glamazdin, A.V. |
| author_sort |
Pomatsalyuk, R.I. |
| title |
Møller polarimeter reconstruction in Hall A Jefferson Lab |
| title_short |
Møller polarimeter reconstruction in Hall A Jefferson Lab |
| title_full |
Møller polarimeter reconstruction in Hall A Jefferson Lab |
| title_fullStr |
Møller polarimeter reconstruction in Hall A Jefferson Lab |
| title_full_unstemmed |
Møller polarimeter reconstruction in Hall A Jefferson Lab |
| title_sort |
møller polarimeter reconstruction in hall a jefferson lab |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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2013 |
| topic_facet |
Элементы ускорителей |
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https://nasplib.isofts.kiev.ua/handle/123456789/111801 |
| citation_txt |
Møller polarimeter reconstruction in Hall A Jefferson Lab / R.I. Pomatsalyuk, V.V. Vereshchaka, A.V. Glamazdin // Вопросы атомной науки и техники. — 2013. — № 6. — С. 48-52. — Бібліогр.: 6 назв. — англ. |
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ISSN 1562-6016. ВАНТ. 2013. №6(88) 48
ACCELERATORS COMPONENTS
MØLLER POLARIMETER RECONSTRUCTION IN HALL
A JEFFERSON LAB
R.I. Pomatsalyuk, V.V. Vereshchaka, A.V. Glamazdin
National Science Center “Kharkov Institute of Physics and Technology”, Kharkov, Ukraine
E-mail: rompom@kipt.kharkov.ua
The Møller polarimeter reconstruction for measuring of the electron beam polarization with energies up to
11 GeV has been performed in Hall A Thomas Jefferson Laboratory (United States). This paper describes the ele-
ments of the Møller polarimeter and accelerator beamline that have been changed. The structure and characteristics
of the modified data acquisition system of the polarimeter are shown. An analysis of components of systematic error
of beam polarization measurement for two types of used targets is presented.
PACS: 29.25.Pj; 29.27.Hj; 29.85.Ca
1. MØLLER POLARIMETER
Møller polarimeter was developed in KIPT and cre-
ated jointly with the National Accelerator Center.
Thomas Jefferson (CEBAF, Virginia, USA) and the
University of Kentucky (Lexington, USA) [1, 2]. The
accelerator of Jefferson Lab [3] is a recirculation super-
conducting electron accelerator (Fig. 1), which consists
of an injector, two of linear accelerators ("northern" and
"southern") bending and extracting magnets, and is ca-
pable deliver a linearly polarized electron beam in three
experimental halls (A, B, C) at the same time. The max-
imum average beam current of accelerator is up to
200 mA, the longitudinal polarization of the beam is up
to 90%, pulse repetition frequency is 499 MHz. The
range of beam energies is from 0.6 to 6 GeV.
Polarimeter designed to measure the polarization of
the beam electrons in the energy range from 0.8 to
6 GeV at a beam current up to 3.0 μA and works in Hall
A starting from 1998 year. The need to modernize the
polarimeter is caused by the reconstruction of the Jeffer-
son Lab accelerator and increasing the electron beam
energy from 6 to 12 GeV.
Experimental Halls
Injector
refrigerator
Hilium
North Linac
600 MeV, 20 cryomodules
600 MeV, 20 cryomodules
South Linac
Bending and
extraction
magnets
Fig. 1. Jefferson Lab accelerator before reconstruction
Møller polarimeter includes polarized electrons tar-
get (T), magnetic spectrometer and detector (Fig. 2).
Møller electrons resulting from the interaction of the
electron beam to the target are analyzed with a magnetic
spectrometer. The spectrometer comprises three quad-
rupole (Q1, Q2, Q3) and one of the dipole magnets (Di-
pole). Scattered electrons are focused by quadrupole
magnets in the horizontal plane at the entrance of the
dipole magnet. The dipole magnet deflects the electrons
down to the detector. Shielding insertion located in the
center of the dipole magnet, through which the primary
electron beam is passing without interaction with the
magnetic dipole field.
Q1 Q2 Q3 Dipole
Detector
а)
б)
Z см
X
с
м
Y
с
м
T Main
Beam
Z см
Scattered
electrons
Fig. 2. Scheme of Møller polarimeter before
reconstruction: а) side view, b) top view
Electron detector consists of two full absorption cal-
orimeters, allowing register the Møller events in coinci-
dences. Each calorimeter made from two identical
blocks type of the "spaghetti", arranged vertically one
above another and divided into two sections. Four pho-
tomultiplier tubes (PMTs) are located at the end of the
calorimeter block. The aperture detector made of plastic
scintillator and divided into four sections installed be-
fore each calorimeter.
Møller events are registered by the coincidence of
signals from the left and right detectors, which can sig-
nificantly reduce the contribution of background events.
2. POLARIMETER PARTS
RECONSTRUCTION
There are several key factors, which are limited en-
ergy range of polarimeter:
- the spectrometer acceptance wich determines by the
position of the magnetic elements, their magnetic
field and the position of the collimator;
- bending of the main beam by a magnetic field of a
dipole inside the shield insertion.
The first factor limits the energy range from below
to 0.8 GeV, and the second one does from the top to
6.0 GeV. To measure the polarization of the electron
beam with energies up to 11 GeV, it was necessary to
a
b
Z cm
Z cm
X
c
m
Y
c
m
ISSN 1562-6016. ВАНТ. 2013. №6(88) 49
reconstructing of the main elements of Møller polarime-
ter. Following elements of the polarimeter have been
modified:
- Magnetic Spectrometer;
- Shielding box of the detector and the detector;
- The elements of beamline;
- Data acquisition system.
The most significant changes required for a magnet-
ic spectrometer of polarimeter. For operation of the po-
larimeter in the energy range 0.8…11 GeV, it was nec-
essary to move the first quadrupole magnet Q1 (Fig. 3)
along the beam by 40 cm and install an additional quad-
rupole magnet Q4 (see Fig. 3) in 70 cm from the target.
The quadrupole magnet Q4 has been installed on beam-
line after testing and measurement of the magnetic field
map.
Fig. 3. New quadrupole magnet Q4 installed behind target
This configuration of the magnetic elements ensures
that acceptance of the polarimeter by solid angle of θcm
more than 20° (Fig. 4) in energy range from 0.8 to
11 GeV.
Reconstruction of the dipole magnet was to improve
the protection of the main beam of electrons from the
magnetic field of the dipole magnet. For his a additional
shielding insertion type of tube made from steel AISI-
1006 with an internal diameter of 2.5 cm and thickness
of 0.9 cm and length of 212.4 cm (Fig. 5) has been
manufactured and installed in the dipole.
Fig. 4. Acceptance of polarimeter by solid angle θcm
for configuration with four quadrupole magnets
The power supply provides a maximum dipole cur-
rent 550 A, which is only enough for the beam energy
up to 8 GeV at Møller electron deflection angle of 10°.
This limitation has led to the need to reduce the maxi-
mum angle of deflection of Møller electron from 10 to
7.3°. Fig. 6 shows the results of the simulation by pro-
gram TOSCA the displacement of the electronic beam
on the physical target in the Hall A ("a" – 13 m from the
center of the dipole) and the beam dump ("b" – 63 m
from the center of the dipole) due to the influence of the
magnetic dipole field with shielding insertion. We can
see that with the maximum energy of the electron beam
in Hall A 11 GeV beam displacement on the main target
of not more than 2.5 mm and not more than 10 mm in
the beam dump. Calculations according to the dipole
magnetic field in the gap and inside the shielding inser-
tion for different energies of the electron beam are
shown in Fig. 7.
Fig. 5. Photo: additional shielding insertion of dipole
Fig. 6. Beam displacement on the physical target (left)
and beam dump (right) due to magnetic field of dipole
with shielding insertion
Fig. 7. Calculation of dipole magnetic field in gap
(upper) and inside shielding insertion for different
electron beam energies
ISSN 1562-6016. ВАНТ. 2013. №6(88) 50
As the deflection angle Møller electrons has been
reduced from 10° to 7.3°, the detector with a shielding
housing box was raised to 7 cm. A new shielding hous-
ing box of detector is designed and manufactured with
improved design of input windows, doors, and the pos-
sibility of placing additional protection at the top of box
near beamline. Support that provides tilt of detector, has
also been replaced for an angle of 7.3°. Aperture coun-
ters modification is performed: added test LEDs, im-
proved light protection and the connection to the PMT.
Elements of beamline after a dipole magnet have al-
so been modified (Fig. 8). Vertical corrector to compen-
sate the bending of the electron beam after the dipole
has been added. An additional beam position sensor has
been added for more precise positioning of the beam on
the target of polarimeter.
Beam position
monitor
Vertical
Corrector
beam
Fig. 8. Additional elements of beam line after dipole
3. POLARIZED ELECTRON TARGET
Two types of polarized targets are used in Møller
polarimeter for measurements of the polarization of the
beam: 1) the target with a low magnetic field (0.03 T)
and polarization along the plane of the target ("Low
Field") [5]; 2) target with a large magnetic field (4 T)
and polarization-zation across the plane of the target
("High Field") [6].
"Low Field" target of polarized electrons comprises
ferromagnetic foil set (Table 1) that inclined at an angle
of 20.5° to the direction of the electron beam and the
magnetic field. The foils have a different thickness and
made of pure iron (99.95%) or supermendur (49% Fe,
49% Co, 2% V).
Table 1
Set of ferromagnetic foils as target of polarized elec-
trons. (SM – supermendur; Fe – iron; Al – aluminum)
Position 6 5 4 3 2 1 0
Material park SM Fe Fe SM SM Al
Thick-
ness, μm
– 6.8 9.3 14.3 29.4 13.0 16.5
The design of the target chamber is shown in Fig. 9.
The design of the camera allows one to move the foil
target in two directions across the beam (from the foil to
the foil), and along the long sides of the foil.
The target chamber is provided with flanges and bel-
lows for mounting on beamline. Magnetic coils are
mounted on the camera symmetrically on either side of
the target.
The target chamber is mounted on slides (see Fig. 9),
inclined at an angle of 20.5° to the direction of the elec-
tron beam. These rails allow a longitudinal movement
of the target relative to the electron beam in the range
from -25 to +30 mm.
The longitudinal position of the target is controlled
by the position sensors and the ree switches. Both
mechanisms moving target are used stepper motors.
Since only a thin target foils can get on the beam, the
change of the target position does not require interrup-
tion of the electron beam.
Fig. 9. The target chamber of Møller polarimeter.
Structure of target holder is shown at above. Direction
of target movement is shown by arrow
The design of "High Field" target of polarized elec-
trons of Møller polarimeter in the Hall A is shown in
Fig. 10. The target consists of:
- Superconducting magnet with a maximum field up
to ± 4 T;
- Target device with a set of four targets. All targets
are made of pure iron with a purity of 99.85% and
99.99% and thicknesses of 1, 2, 4, and 10 μm to the
study of possible systematic errors;
- Adjustment mechanism for the orientation of the
plane of the target relative to the direction of the
magnetic field;
- Unit for movement and control targets position;
- The target chamber with orientation mechanism to
the direction of the magnetic field along the electron
beam.
beam
Fig. 10. The design of "High Field" target of polarized
electrons of Møller polarimeter in the Hall A.
The diagram shows: a superconducting magnet,
the target device and the target camera. The photo
shows the target holder with a set of iron foils
ISSN 1562-6016. ВАНТ. 2013. №6(88) 51
Adjustment mechanisms allow set of the target de-
vice and the magnetic field with linear precision
± 0.2 mm and angular accuracy of ± 0.2 mrad.
4. DATA ACQUISITION SYSTEM
The data acquisition system of the Møller polarime-
ter used over 15 years [4]. Some of the electronic mod-
ules are already discontinued. Acquisition system was
modified to increase readout rate and reduce dead time.
Basic electronic modules have been replaced with mod-
ern one, with more high integration and a high frequen-
cy bandwidth.
The module type of CAEN V1495 is used as pro-
grammable logic unit: bandwidth input/output of up to
200 MHz, 2 32-bit input ports, 1 output port, 32-bit,
type of signal - LVDS; programmable logic (Fig. 11).
Fig. 11. Diagram of programmable logic unit based
on module type of CAEN V1495
The module contains a programmable logic for event
selection (16 inputs, 16 outputs), 16 counters (32-bit),
trigger logic, control registers, and timer-generator.
Discriminator P / S 708: 8 channels, 300 MHz signal
type - NIM, modified for remote setup of thresholds
using the digital to analog converter (DAC).
Analog-to-digital converter (ADC) type of CAEN
V792: 12 bit, 32 channel, memory 32 events, the con-
version time is 5.7 μs.
The time to digital converter module (TDC) type of
CAEN V1190B: 64 channels, the resolution is 0.1 ns,
the signal type - LVDS.
Test of new modules has been performend and soft-
ware developing for data processing is underway.
5. MØLLER POLARIMETER SYSTEMATIC
ERRORS
The main components of the systematic errors of po-
larimeter for the two types of targets that affecting the
accuracy of measurements of the beam polarization are
shown in Table 2. It can be seen that the main contribu-
tion to the target with a low field gives a measurement
error of the target polarization. For target with a large
field, this error is greatly reduced, due to a stronger
magnetisation of foil that close to saturation. At the
same time, the Levchuk effect is increased for this type
of target due to the stronger magnetic field.
Table 2
Systematic errors of Møller polarimeter for two types
of target
Variable
“Low
Field”
target, %
“High
Field”
target, %
Target Polarization 1.5 0.35
Analyzing power 0.3 0.3
Levchuk effect 0.2 0.3
Dead Time 0.3 0.3
Background 0.3 0.3
High Beam Current 0.2 0.2
Others 0.5 0.5
Total 1.7 0.9
CONCLUSIONS
Møller polarimeter in Hall A of Jefferson Laboratory
(USA) was reconstructed in the period 2012-2013 for
measurements of electron beam polarization with ener-
gies up to 11 GeV. This paper describes the elements of
the Møller polarimeter and accelerator beamline, which
have been modified. The polarimeter is a unique facility
with two different types of polarized targets and the two
types of data acquisition systems working in parallel.
This allows us to investigate the systematic uncertainty
and improve the accuracy of measurements of electron
beam polarization.
This work was supported by contract
DE-AC05-06OR23177 the U.S. Department of Energy
on the basis of which Jefferson Science Associates oper-
ates the Thomas Jefferson National Accelerator Facility.
REFERENCES
1. A.V. Glamazdin, V.G. Gorbenko, L.G. Levchuk, et
al. Electron Beam Møller Polarimeter at Jlab Hall A
// Fizika. 1999, B8, p. 91-95 (in Russian).
2. E.A. Chudakov, A.V. Glamazdin, V.G. Gorbenko,
L.G. Levchuk, R.I. Pomatsalyuk, P.V. Sorokin.
Møller polarimeter for electron beam in Hall A Jef-
ferson Lab // Problems of Atomic Science and Tech-
nology. Series «Nuclear Physics Investigations».
2002, №2(40), p. 43-48.
3. W. Leemann, David R. Douglas, Geoffrey A. Krafft.
The Continuous Electron Beam Accelerator Facility:
CEBAF at the Jefferson Laboratory // Annu. Rev.
Nucl. Part. Sci. 2001, v. 51, p. 413-450.
4. R.I. Pomatsalyuk. Data Acquisition System of
Møller Polarimeter Hall A Jefferson Lab // Problems
of Atomic Science and Technology. Series «Nuclear
Physics Investigations». 2012, №3(79), p. 101-104.
5. O.V. Glamazdin, E.A. Chudakov, R.I. Pomatsalyuk.
Hall A Møller polarimeter (Jefferson Lab) with elec-
tron target polarized in foil plane // Journal of Khar-
kov University. Physical series «Nuclei, Particles,
Fields». 2011, №2(50), v. 955, p. 42-50.
ISSN 1562-6016. ВАНТ. 2013. №6(88) 52
6. A.V. Glamazdin. Hall A Muller Polarimeter (Jeffer-
son Laboratory) after reconstruction // Problems of
Atomic Science and Technology. Series «Nuclear
Physics Investigations». 2012, №4(80), p. 7-10.
Article received 07.10.2013
МОДЕРНИЗАЦИЯ МЁЛЛЕРОВСКОГО ПОЛЯРИМЕТРА ЗАЛА А ЛАБОРАТОРИИ
им. Т. ДЖЕФФЕРСОНА
Р.И. Помацалюк, В.В. Верещака, А.В. Гламаздин
В лаборатории им. Т. Джефферсона (США) проведена реконструкция мѐллеровского поляриметра зала А
для обеспечения измерений поляризации пучка электронов с энергией до 11 ГэВ. В работе описаны элемен-
ты мѐллеровского поляриметра и электронопровода ускорителя, которые были изменены. Приведены струк-
тура и характеристики модифицированной системы сбора данных поляриметра. Проведѐн анализ величины
систематической ошибки измерения поляризации пучка для двух типов используемых мишеней.
МОДЕРНІЗАЦІЯ МЬОЛЛЕРІВСЬКОГО ПОЛЯРИМЕТРА ЗАЛУ А ЛАБОРАТОРІЇ
ім. Т. ДЖЕФФЕРСОНА
Р.I. Помацалюк, В.В. Верещака, О.В. Гламаздін
У лабораторії ім. Т. Джефферсона (США) проведено реконструкцію мьоллерівського поляриметра залу
А для забезпечення вимірювань поляризації пучка електронів з енергією до 11 ГеВ. У роботі описані елеме-
нти мьоллерівського поляриметра та електронопровода прискорювача, які були змінені. Наведено структуру
та характеристики модифікованої системи збору даних поляриметра. Проведено аналіз величини системати-
чної помилки вимірювання поляризації пучка для двох типів мішеней, що використовувались.
|