PROPOSAL 2006 - G.I.A.F. (HYBRID GUN AT HIGH FREQUENCY) INFN-LNF – UNIVERSITY OF ROME “LA SAPIENZA”- UCLA D. Alesini (T), M. Ferrario (R), A. Gallo (T),

PROPOSAL 2006 - G.I.A.F. (HYBRID GUN AT HIGH FREQUENCY)

INFN-LNF – UNIVERSITY OF ROME “LA SAPIENZA”- UCLA

• D. Alesini (T), M. Ferrario (R), A. Gallo (T), F. Marcellini (T), V. Fusco (art. 23), B. Spataro (T) (Resp. Naz.)

• LNF Full Time Equivalent 1.5 (1.3 tecnologist – 0.2 researcher)

• L. Ficcadenti (D), M. Esposito (AU), M. Migliorati (R), A. Mostacci (consultant), L. Palumbo (PO)

• University of Rome Full Time Equivalent 1.2 (0.6 tecnologist – 0.6 researcher)

• J. Rosenzweig(PO)• UCLA Dept. of Physics and Astronomy Full Time Equivalent 1.0

(R)

TOTAL FTE 3.7

HYBRID GUN ELECTROMAGNETIC DESIGN

AND RF MEASUREMENTS

2) DESIGNED STRUCTURES:

a) Integrated accelerating structure;

b) Integrated velocity bunching (acceleration+longitudinal bunch compression);

3) POSSIBLE MEASUREMENTS ON PROTOTYPES

1) THE HYBRID STRUCTURE: ADVANTAGES

SW 1.6 Cell Gun

Input Cell

Emittance-CompensatingSolenoids

Cathode

TW structure

Input Port

1) THE HYBRID STRUCTURE

1) Eliminate transient reflection associated with SW structures (especially needed for X-band);

2) Compactness: -simplicity (RF distribution system, etc.)

-energy efficiency from TW section

3) Promising good beam dynamics in term of beam emittance and reachable bunch length (velocity bunching)

1) THE HYBRID STRUCTURE: ADVANTAGES

2) DESIGNED STRUCTURES: GENERAL CONSIDERATIONS

The steps to design the structure are the following:

a) “Separate” tuning of the SW and TW sections in order to achieve a uniform field flatness of the E field in the SW gun and a zero reflection coefficient at the waveguide input port of the TW section at the working frequency of the whole system;

b) Final tuning of the whole structure to put the SW section perfectly on resonance with a uniform field flatness of the E field in the first two cells;

1) the phase of the E field between the SW gun and the TW section does not depend on the geometry of the input coupler cell, iris dimensions,… and is about 90 deg. This results has been found by 3D electromagnetic simulations and has been justified with an equivalent circuit model;

2) the coupling iris aperture between the input coupler cell and the SW structure allows adjusting the ratio beween the amplitude of the fields in the SW cells and in the TW section: in particular if we increase the radius we increase this ratio;

RESULTS (S-Band Case)

E.M. field characteristics @ gun resonance

Input coupler cell

90 deg

Ez(z,t)=E0(z)cos(ph(z)+t)

Mode of the gun

4) Since the phase between the SW structure and the TW one is fixed, the synchronism between the accelerating field and the bunch passage can be adjusted by properly chosing the lenght of the input coupler cells. It is therefore possible to design two different structure:-the first one obtainded choosing Dc=2/3 in which the beam is accelerated in both structures SW gun and and TW section;-the second one obtained by choosing Dc=5/12 in which the bunch is accelerated in the SW section and longitudinally compressed (velocity bunching technique) in the TW one;

Dc

3) for reasonable values of the coupling iris (that gives a ratio between the amplitude of the fields up to 5) the perturbation on the matching of the input coupler waveguide is completely negligible.

0.5deg/kHz

Integrated velocity bunching (1/2)

Amplitude of the E field along the structure (E0(z))

Phase (ph(z)) of the electric field along the structure: the sensitivity of the phase with respect to the resonant frequency of the SW structure requires very good stabilization of the temperature or an RF feedback

Ez(z,t)=E0(z)cos(ph(z)+t)

Eacc

z z

Inputcoupler

Outputcoupler

Traveling wave structure

zbunch

Integrated velocity bunching (2/2)

EaccEacc

Integrated velocity bunching dimensions

ac

bc

dc

t

ab

d

aw bw/2

w/2

hbf

bh

df

dh

tg

tc

ag

ac 9 [mm]

tc 19.05

bc 40.93

dc 43.74

t 8

a 16

b 42.89

d 34.99

h 2

aw 30.21

bw 72.14

bf 41.7

df 52.48

tg 19.05

ag 12.5

bh 41.67

dh 31.49

w 35.2

Integrated accelerating structure dimensions

ac

bc

dc

t

ab

d

aw bw/2

w/2

hbf

bh

df

dh

tg

tc ag

ac 9 [mm]

tc 19.05

bc 40.53

dc 69.98

t 8

a 16

b 42.89

d 34.99

h 2

aw 36.09

bw 72.14

bf 41.7

df 52.48

tg 19.05

ag 12.5

bh 41.67

dh 31.49

w 33.3

3) RF MEASUREMENTS

Steele method (C.W. Steele, IEEE trans. on micr th. and tech., 1965) is applicable to SW and to TW structures separately;

Difference between the reflection at the input port with and without the perturbing object at z longitudinal position

Pertubing objects

Hybrid gun NA

zph22011

je ezEKzS

z

zS11

PARMELA simulations Input Beam Parameters:

Q=1 nC

LTW=3 m

T0 =10 psec

Rb=1.57 mm

0=40 deg

Magnetic field

Energy gain and Momentum spread evolution

Bunch length and Transverse beam size evolution

Emittance evolution

SPARC (S Band) HYBRID (S Band)

Mode Normal RF Compr.

Normal RF Compr.

Total Length [m] 12 12 3 3

Energy [MeV] 220 180 50 22

Energy Spread [%] 0.1 1.0 0.3 1.5

Peak Current [A] 100 800 100 400

Rms norm. emittance [m] <2 <2 <2 <4

Work planning 2007

1 Design of the hybrid structure at 3 GHz (velocity bunching);

2 Construction of a prototype at 3 GHz with no cooling and brazing for the measurements at room temperature; beam dynamic simulation ;

3 Some tests for brazing on some cells.

2008

1 Design of the hybrid structure at 11 GHz (velocity bunching);

2 Construction of a prototype at 11 GHz with no cooling and brazing for the measurements at room temperature; beam dynamic simulation ;

3 Tests for brazing on some cells.

2009

1 Design of a hybrid structure at 11 GHz included the cooling system;

2 Construction of a brazed hybrid structure and measurements at room temperature;

3 High power tests for structures at 3 GHz and 11 GHz

Estimates costs2007 Costs ( 3 GHz)

1 hybrid structure 61.0 KEuro

2 waveguide tapers 10.0 KEuro

Brazing tests 5.0 KEuro

Consumable 3.0 KEuro

Durable equipment 8.0 KEuro

2008 Costs (11 GHz)

1 hybrid structure 37.0 KEuro

2 waveguide tapers 8.0 KEuro

Brazing tests 5.0 KEuro

Consumable 3.0 KEuro

Durable equipment 8.0 KEuro

2009 Costs (11 GHz)

1 hybrid structure 90.0 KEuro

2 waveguide tapers 10.0 KEuro

Brazing tests 5.0 KEuro

Consumable 13.0 KEuro

Durable equipment 8.0 KEuro

Domestic travel/year 2.0 KEuro

Abroad travel/year 5.0 KEuro

SUMMARY COSTS

Domestic travel (KEuro)

Abroad travel

(KEuro)

Consumable

(KEuro)

Durable equipment

(KEuro)

Equipment constructions

(KEuro)

2007 2.0 10.0 8.0 8.0 71.0

2008 2.0 10.0 8.0 8.0 40.0

2009 2.0 10.0 13.0 8.0 90.0

Total 6.0 30.0 29.0 24.0 201.0

Consumable : attenuator, connectors, cables, vacuum components (flanges, gaskets, valves), ceramic transitions, brazing alloys etc.

Durable equipments : guide transitions, loads, directional coupler, power supply

Equipment constructions : hybrid structure included 2 waveguide tapers