High-precision beam profile monitor for the DESY Н-minus linac
Збережено в:
| Дата: | 1999 |
|---|---|
| Автори: | , , , , , , , , , , |
| Формат: | Стаття |
| Мова: | English |
| Опубліковано: |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України
1999
|
| Назва видання: | Вопросы атомной науки и техники |
| Онлайн доступ: | http://dspace.nbuv.gov.ua/handle/123456789/81532 |
| Теги: |
Додати тег
Немає тегів, Будьте першим, хто поставить тег для цього запису!
|
| Назва журналу: | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| Цитувати: | High-precision beam profile monitor for the DESY Н-minus linac / V.A. Gaidash, Y.N. Gotovtsev, A.A. Menshov, P.N. Ostroumov, N. Holtkamp, М. Nagl, C.M. Kleffner, J. Maidment, I. Peperkorn, J. Rothenburg, B. Sarau // Вопросы атомной науки и техники. — 1999. — № 4. — С. 57-59. — Бібліогр.: 7 назв. — англ. |
Репозитарії
Digital Library of Periodicals of National Academy of Sciences of Ukraine| id |
irk-123456789-81532 |
|---|---|
| record_format |
dspace |
| spelling |
irk-123456789-815322016-04-14T11:12:22Z High-precision beam profile monitor for the DESY Н-minus linac Gaidash, V.A. Gotovtsev, Y.N. Menshov, A.A. Ostroumov, P.N. Holtkamp, N. Nagl, М. Kleffner, C.M. Maidment, J. Peperkorn, I. Rothenburg, J. Sarau, B. 1999 Article High-precision beam profile monitor for the DESY Н-minus linac / V.A. Gaidash, Y.N. Gotovtsev, A.A. Menshov, P.N. Ostroumov, N. Holtkamp, М. Nagl, C.M. Kleffner, J. Maidment, I. Peperkorn, J. Rothenburg, B. Sarau // Вопросы атомной науки и техники. — 1999. — № 4. — С. 57-59. — Бібліогр.: 7 назв. — англ. 1562-6016 http://dspace.nbuv.gov.ua/handle/123456789/81532 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| institution |
Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| collection |
DSpace DC |
| language |
English |
| format |
Article |
| author |
Gaidash, V.A. Gotovtsev, Y.N. Menshov, A.A. Ostroumov, P.N. Holtkamp, N. Nagl, М. Kleffner, C.M. Maidment, J. Peperkorn, I. Rothenburg, J. Sarau, B. |
| spellingShingle |
Gaidash, V.A. Gotovtsev, Y.N. Menshov, A.A. Ostroumov, P.N. Holtkamp, N. Nagl, М. Kleffner, C.M. Maidment, J. Peperkorn, I. Rothenburg, J. Sarau, B. High-precision beam profile monitor for the DESY Н-minus linac Вопросы атомной науки и техники |
| author_facet |
Gaidash, V.A. Gotovtsev, Y.N. Menshov, A.A. Ostroumov, P.N. Holtkamp, N. Nagl, М. Kleffner, C.M. Maidment, J. Peperkorn, I. Rothenburg, J. Sarau, B. |
| author_sort |
Gaidash, V.A. |
| title |
High-precision beam profile monitor for the DESY Н-minus linac |
| title_short |
High-precision beam profile monitor for the DESY Н-minus linac |
| title_full |
High-precision beam profile monitor for the DESY Н-minus linac |
| title_fullStr |
High-precision beam profile monitor for the DESY Н-minus linac |
| title_full_unstemmed |
High-precision beam profile monitor for the DESY Н-minus linac |
| title_sort |
high-precision beam profile monitor for the desy н-minus linac |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
1999 |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/81532 |
| citation_txt |
High-precision beam profile monitor for the DESY Н-minus linac / V.A. Gaidash, Y.N. Gotovtsev, A.A. Menshov, P.N. Ostroumov, N. Holtkamp, М. Nagl, C.M. Kleffner, J. Maidment, I. Peperkorn, J. Rothenburg, B. Sarau // Вопросы атомной науки и техники. — 1999. — № 4. — С. 57-59. — Бібліогр.: 7 назв. — англ. |
| series |
Вопросы атомной науки и техники |
| work_keys_str_mv |
AT gaidashva highprecisionbeamprofilemonitorforthedesynminuslinac AT gotovtsevyn highprecisionbeamprofilemonitorforthedesynminuslinac AT menshovaa highprecisionbeamprofilemonitorforthedesynminuslinac AT ostroumovpn highprecisionbeamprofilemonitorforthedesynminuslinac AT holtkampn highprecisionbeamprofilemonitorforthedesynminuslinac AT naglm highprecisionbeamprofilemonitorforthedesynminuslinac AT kleffnercm highprecisionbeamprofilemonitorforthedesynminuslinac AT maidmentj highprecisionbeamprofilemonitorforthedesynminuslinac AT peperkorni highprecisionbeamprofilemonitorforthedesynminuslinac AT rothenburgj highprecisionbeamprofilemonitorforthedesynminuslinac AT saraub highprecisionbeamprofilemonitorforthedesynminuslinac |
| first_indexed |
2025-07-06T06:33:03Z |
| last_indexed |
2025-07-06T06:33:03Z |
| _version_ |
1836878229744386048 |
| fulltext |
HIGH-PRECISION BEAM PROFILE MONITOR FOR THE DESY
H-MINUS LINAC
V.А. Gaidash*, Y.N. Gotovtsev*, A.A. Menshov*, P.N. Ostroumov*, N. Holtkamp, М. Nagl,
C.-M. Kleffner, J. Maidment, I. Peperkorn, J. Rothenburg, B. Sarau
*Institute For Nuclear Research, Moscow, Russia
DESY, Hamburg, Germany
INTRODUCTION
Three diagnostic boxes (Dbox3, Dbox4 and
Dbox5, see Fig.1) with DMH14, DMH17, DMH20 wire
harp monitors respectively have been developed in INR
and installed in the DESY 50 MeV H- Beam Transport
Line, called HEBT, guide the H- beam from Linac III
over 80 m to the injection part of the synchrotron DESY
III.
Fig.1. DESY 50 MeV H- Beam Transport Line (HEBT).
The harp is based on the principle of secondary
emission of loosely bound electrons on the surface of
the wires as proton beam passes through them. The
secondary emission signal is linear over a wide dynamic
range of incident protons and is measured by the
electronics connected to each wire [2]. The two
electrons stripped from the impinging H- Ions have a
range of less than 2 µm and are thus quantitatively
collected. The expected charge factor of 2.0 is reduced
by secondary electrons leaving the wire; their effect,
however, is suppressed by a bias voltage applied to
three grids which enclosed the two signal planes [1].
The presented profile monitor is differed in the
use of tungsten microwire dW = 20 µm a dia as a
irradiated contact elements. Unfortunately, it has
presented some difficulties in fixing of wire. The choise
of fixing method depends on intensity of beam and
corresponding heating balance of wire. The use of more
thin wires decrease a temperature of their heating during
beam pulse. More thin wires with smaller mass m will
absorb to smaller thermal energy q and, in accordance
with relation q = m⋅c⋅θ, will heat with the smaller
temperature drop θ, where c is a specific heat capacity.
The long-time stability of a wire heating balance is
determined by limitations of maximum heating
temperature and a limitation of a temperature gradient
during a beam pulse. The maximum heating temperature
Tmax should not exceed melting point of a tungsten.
However, first of all, Тmax should be less than
temperature of a distorting signal of a thermionic
current, which is determined by magnitude
Тмах ≤ 1700 К according to the Richardson - Dashman
formula. The safe temperature drop θmax ≤ 1116 К is
recommended for the tungsten during the cyclic heating
by beam pulses. Then the ultimate thermal energy of
heating is restricted to magnitude qmax = m⋅cT⋅θmax, where
cT is specific heat at Тмах. Therefore, during a beam
pulse t0 [s] the absorbable energy in the wire should be
such, that the thermal energy, transferred to a wire, did
not exceed the magnitude q0 ≈ dE⋅(dz)- 1⋅dW⋅∆Ia⋅t0 < qmax
[3]. In this relation ∆Ia is the part of a beam current on
the active area of one wire [А], power loss Е [eV] is
evaluated by a specific stopping power of a tungsten dE
⋅(dz)-1 on the penetration depth dz [m] according to the
Bethe - Bloch formula. Both the heat balance of a wire
during cyclic heating by beam pulses and the
consecutive cooling by radiation - thermal conduction
between adjacent pulses is determined by a step-by-step
calculation.. The decrease of wire temperature Tn [K] is
determined upon a remainder of unaverted thermal
energy qn-1 [J] for each time interval dtn [s] in time
interval τ [s] between adjacent pulses by the relation
TWa
2
W
n1nT
1
x
2
Wn
94
1nTaW1n
n crd78,0
dtld78,0dt)107T(rdq5,0T
⋅⋅⋅⋅
⋅⋅⋅⋅⋅−⋅⋅−⋅⋅⋅⋅⋅−⋅= −
−
−−
ρ
θλσεπ
where ra - radius of a beam [m]; εT - emissive power
coefficient of a tungsten; σ =5,67⋅10-8 J⋅s-1⋅К-1⋅m-2 -
Stefan-Boltzmann constant; lx - length of unirradiated
("cold") wire ends [m]; ρW - density of a tungsten [kg⋅
m-3]; λT - thermal conductivity of a tungsten at
temperature Tn [J⋅s-1⋅К-1⋅m-1]; cT - specific heat of a
tungsten at temperature Tn. [J⋅kg-1⋅К-1].
The diagram of the steady-state heating balance
of 20 µm a dia tungsten wire is shown in Fig.2.
THE DESIGN
The profile monitor has a vacuum chamber with
a stand-base plate, an actuator with a stepper motor and
a harp unit (Fig 3). The wire harp unit installed on a
actuator which is tilted by 45° relative to horizontal in
order to provide simultaneous movement in both x and y
directions.
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 1999. № 4.
Серия: Ядерно-физические исследования (35), с. 57-59.
57
293
500
θ 0
Τ 0 t0
n⋅ τ
t0τ
700
900
1100
1300
1500
1700
n⋅ τ + 4 n⋅ τ + 8
t0
n⋅ τ + t, cTW.
Τ max
T, K
Fig.2. Heating balance diagram for 20 µm a dia tungsten
wire at steady-state cycling mode during 15 mA 50 MeV
H- beam pulse: TW – wire remperature [K]; t0 = 200 µs –
pulse length; τ = 4 s – interval between adjacent
macropulses; Tmax – maximum adjacent wire
temperature [K]; t – measurement time [s].
The vacuum chamber consists of the body and
two end plates. The thick-wall forging tube from
stainless steel was used for fabrication of the body. It
has only one weld seam and two CF-250 connections
with end plates through copper gaskets. Other sides of
end plates are CF-100 conflat flanges for connection
with HEBT flanges.
The actuator uses a 5-phase stepper motor of the
VRDM 5913/50 type. It produces 1000/500 steps per
turn (0,36°/0,72° ± 3′ per step) for half step / all-step
mode respectively [5]. The actuator drives the harp unit
at 6.15 mm/s along the x and y axes when it is operated
at its maximum speed. The maximum stroke is
104.5 mm. The rotation of the motor shaft is
transformed through rigid branch sleeve into the
displacement of the Linear Motion Guide Actuator
KR2602A plate, the positioning repeatability is ± 10 µm
[6]. The membrane bellows is used as vacuum seal. The
rod of the actuator is terminated with the rotatable
CF-35 flange to which the CF-35 flange of harp unit is
fixed. The minimum displacement per step along the x-
and y-axes is 1.4 (2.8) µm for half-step (all-step) mode
respectively.
Each harp unit is a stack of five rings with 130
mm O.D. and 90 mm I.D. from a machinable mica-glass
ceramics, which are clamped together to form a rigid
assembly of 19 mm thick. A final assembly mounted on
a aluminium body is shown in Fig.4. Each harp has two
signal and three bias grids of sixteen and 26 gold-plated
thin (20 µm) tungsten wires respectively. As the heating
is insignificant during a beam pulse (see Fig. 2), the
wires was soldered by chemically pure tin with a
tension on each wire ~ 30 g. The contact lands was
made by printed-circuit technique after vacuum
evaporation of 2-6 µm copper. Then copper layer of
obtained lands was increased up to ~20 µm by
electroplating. A grounded 2-6 µm layer of silver is
evaporated on the backside of every bias and signal
ceramic ring to intercept possible leak currents. The
wires signal are fed through ∅ 0.5 mm silver-plated
copper wire with crimped contacts to 48-pin
KYOCERA Ultra High Vacuum Feedthrough and a
shielded cable of about 1 m length to two 8-hold
preamplifiers with a gain of 1 V /30 µA. The output
signals of up to +10 V travel on twisted pair lines to
active signal distributors (Fig.5) [1].
Fig.3. Beam profile monitor for DESY H- Linac III.
Fig.4. Assembly view of the harp unit.
58
1 2 43 7 865 9 10 11 12 13 14 15 16
GND
S/H
A
D
C
T
I
M
E
R
D
A
C
BIASPS 0 - 300 V
Monitor
Buffer
SEDAC
15 Channel
Timer Unit
SEDAC
15 Channel
Timer Unit
SEDAC
Dual 8 Channel
S&H - ADC
Monitor
Amplifier
GND
8 X 8 X 8 X 8 X
GND
X Y GND GND HV
To Computer
10
3 1,5
1615141312111095 6 873 421
S/H
A
D
C
S/H
A
D
C
A
D
C
S/H
Fig.5. Simplified block diagram of the harp electronics.
BEAM MEASUREMENTS
A special drift space with three double wire
harps, is foreseen to measure all six transverse beam
parameters. The profiles recorded by the harps are
approximated by a Gaussian plus a flat background. The
fitted 90% widths are used to compute the beam
parameters β, α and ε on-line [1].
The secondary emission current is integrated and
digitized for each proton beam macropulse. The
computer-controlled data-acquisition system has the
capability of subtracting a costant level of background
and of averiging several measurements. Fig.6 shows a
set of profiles obtained by harp monitors. The proton
beam had a peak intensity of 25 mA and consisted of
200 µs macropulses at 0.25 Hz.
Fig.6. Wire harp profiles.
CONCLUSION
The presented harp monitor allows an almost
non-destructive observation of the beam profiles, and
therefore a permanent online evaluation of the beam
parameters. Every (double) harp intercepts about 3% of
the beam, resulting in a 9% for the 3-harp measurements
[1]. Given all parts and details of monitor has been
made from inorganic materials, we succeeded to obtain
high vacuum properties (the minimum number of weld
seems and conflat-type connections also assisted in it).
We tried to standardize elements of a profile monitor as
much as possible. All movable elements may be
remotely controllable and position may be measurable
with appropriate precision by computer. The spatial
resolution of harp monitors reaches a 1.4 µm and with
fast electronics, bunches can be observed individually.
Their great sensitivity followed by the multi-gain
amplifier allows the study of halos [7]. The designed
profile monitors is a precision device for adjusting the
beam, for emittance measurements [4] and for matching
the phase space ellipses of the beam to the phase space
ellipses of the HEBT line.
REFERENCES
1. L. Criegee. The 50 MeV H- Beam Transport line.
DESY PLIN-Note 89-08, 1989.
2. W.T.Weng et al. The Multiwire Secondary Emission
Monitor and The Emittance Measurement Of The AGS
Beam. IEEE Trans., Vol. NS-30, No. 4, 1983,
p. 2331-2333.
3. O.Dubois, M.Roering. Restrictions of the Use of
Wires as Beam Targets Due To Damage By Heating.
CERN-PS/HP/Note 97-26. Geneva, 1997.
4. L. Criegee. Emittance measurement for Linac III.
DESY PLIN - Note 88-04, 1988.
5. 5-Phasen-Schrittmotoren in 10 Litzen-Technik.
BERGER LAHR Catalog Nr. 3501 D, Lahr, 1994.
6. Super Compact and Rigid Miniature Actuator Type
KR. Catalog No. 203-1E, THK Co., Ltd., Tokyo, 1995.
7. O.R. Sander et al. Recent Improvement in Beam
Diagnostic Instrumentation. IEEE Trans., Vol. NS-26,
No. 3, 1979, p. 3417.
59
|