1. Enrica Chiadroni LNF-INFN 20 aprile 2010
THz Planning 2010
Enrica Chiadroni
LNF-INFN
20 aprile 2010

2. Characterization of TERASPARC
Pyro-electric or Golay cell detectors
Operating spectral range: 0.1 – 3 THz
Active element: 2 mm x 3 mm
Sensitivity: Hz ~ 10-8 W/Hz0.5
Fast time response: tens of us
Operating spectral range: > 40 GHz
Active element: ø 6 mm (diamond window)
Sensitivity: Hz ~ W/Hz0.5
Slow time response: few tens of ms

3. Enrica Chiadroni (INFN-LNF)
Optical Components
Detector
y-Dy z
Filters/
polarizer
x, y
70 mm
electrons z
CTR (30x30 mm, 300 mm SiO2, nm Al) y
90° off-axis parabolic mirrors:
Ø 50.8 mm
EFL mm
z-cut quartz window:
Ø 60 mm, 4.8 mm thick
Enrica Chiadroni (INFN-LNF)

4. Enrica Chiadroni (INFN-LNF)
Optical Components
Detector
y-Dy z
Filters/
polarizer
x, y
70 mm
electrons z
CTR (30x30 mm, 300 mm SiO2, nm Al)
Pyrodetector black polyethylene window y
Enrica Chiadroni (INFN-LNF)

5. I Step: THz Radiation from HB Velocity Bunched EB
Two working points have been investigated
On crest operation
Q = 500 pC
Energy= 167 MeV
energy spread = 0.1%
ex= 3.5 mm mrad
bx = m
ax = -1.17
ey = 4.1 mm mrad
by = 25 m
ay = -2.78
st = 2.0 ps
Compression Factor 4
Q = 500 pC
Energy= 94 MeV
energy spread = 1%
ex= 6.4 mm mrad
bx = 28.4 m
ax =
ey = 3.3 mm mrad
by = m
ay =
st = 0.5 ps
Enrica Chiadroni (INFN-LNF)

6. Enrica Chiadroni (INFN-LNF)
On crest Beam
F(w)
Charge (a.u.)
Frequency (Hz)
Time(ps)
RFD
Flag
On crest operation
Position on the screen (mm)
Enrica Chiadroni (INFN-LNF)

7. Position on the screen (mm)
Compressed Beam
F(w)
Charge (a.u.)
Frequency (Hz)
Time(ps)
RFD VB
Flag
The steepest rising front of the experimental profile allows a greater extension of the
spectrum to higher frequencies with respect to an ideal Gaussian profile.
Position on the screen (mm)

8. Measurements and Results -Pyro-detector-
Detector signal analysis
No compression and compression factor 4
with filters: 0.3 THz, 1.5 THz
Statistical analysis to evaluate fluctuations
Dependence of CTR intensity on N2f(w)
Enrica Chiadroni (INFN-LNF)

9. Effect of Bunch Compression
A gain of a factor 25 in intensity with respect to the on crest operation has been detected in the RF compression mode
--- Compressed bunch
(st = 0.5 ps)
--- Non Compressed bunch
(st = 2.0 ps)
Time (s)

10. Investigating the Spectral Emission Enrica Chiadroni (INFN-LNF)
-On Crest Operation-
C1 with 0.3 THz filter
Enrica Chiadroni (INFN-LNF)

11. Investigating the Spectral Emission
red curve: CTR energy at 350 GHz with a BW of nearly 50 GHz
green curve: broad band CTR energy (up to 3 THz)

12. Investigating the Spectral Emission Enrica Chiadroni (INFN-LNF)
red curve: CTR energy at 1.5 THz with a BW of nearly 0.3 THz
blue curve: broad band CTR energy (up to 3 THz)
Enrica Chiadroni (INFN-LNF)

13. Investigating the Spectral Stability
No filter
Emean = mJ
sE = 0.73 mJ
No filter
Emean = 9.5 mJ
sE = 1.0 mJ
Filter 1.5 THz
Emean = 1.60 mJ
sE = 0.23 mJ
Filter 0.3 THz
Emean = 0.80 mJ
sE = 0.1 mJ

14. Enrica Chiadroni (INFN-LNF)
Shot-to-Shot e-beam fluctuations affect the THz pulse stability;
Typical fluctuations of THz around 10 % due mostly to charge (particle number) instability
Charge fluctuations
5% fluctuations
Enrica Chiadroni (INFN-LNF)

15. Investigating the N2 Dependency Enrica Chiadroni (INFN-LNF)
Charge (pC)
Bunch Length (ps)
125
1.81+/-0.019
225
1.96+/-0.018
335
2.22+/-0.021
490
2.49+/-0.034
Enrica Chiadroni (INFN-LNF)

16. Measurements and Results -Golay cell detector-
Detector signal analysis
No compression and compression factor 8
with filters: THz
On crest operation
Q = 260 pC
Energy= 140 MeV
energy spread = 0.1%
ex= 2.26 mm mrad
bx = 18.8 m
ax =
ey = 1.95 mm mrad
by = 17.9 m
ay =
st = 2.0 ps
Compression Factor 8
Q = 260 pC
Energy= 102 MeV
energy spread = 1%
ex= 4.00 mm mrad
bx = 21.4 m
ax =
ey = 2.96 mm mrad
by = 28.6 m
ay =
st = 0.25 ps
Enrica Chiadroni (INFN-LNF)

17. Measurements and Results -Golay cell detector-
Enrica Chiadroni (INFN-LNF)

18. Measurements and Results -Golay cell detector-
Enrica Chiadroni (INFN-LNF)

19. THz Planning 2010 Week I-II Week III Week IV Week V-VI
Characterization of THz source for different wavelengths with Golay cell detector
Week III
Optimization of THz source for different LINAC settings
Week IV
Setting interferometers (both Martin-Puplett and Michelson) up for frequency measurements and electron bunch characterization
Week V-VI
Upgrade of the experimental layout (i.e. diamond viewport, optical components for pump and probe experiments, N2 flushing, etc.)
Week VII-VIII-IX
Pump and probe experiments to measure the lifetime of an excited level in quantum wells Ge/Si-Ge