Transcript Diapositiva 1

Livio Gianfrani
Molecules and Precision Measurements Research Group
Dipartimento di Matematica e Fisica
Seconda Università di Napoli
Caserta
Consiglio di Sezione INFN, Napoli, 12 July 2016
Andrea Vacchi
INFN Trieste
FAMU Collaboration Meeting, 7-9 June 2016, Trieste, ICTP
Proton charge radius inconsistency
CODATA evaluation of
spectroscopic data on 24
lines of H and D
CODATA 2010
recommended
value
elastic electronproton scattering
experiments
Muonic hydrogen
CREMA
collaboration
Isotopic-shift measurement
of the 1s − 2s transition in
hydrogen and deuterium
MAMI:
Mainzer Mikrotron
Savely G. Karshenboim, Accuracy of the optical determination of the proton charge radius,
Phys. Rev. A 91, 012515 (2015)
Basic ideas
(mp)ns
dQED
dstr
→
→
QED corrections
nuclear structure contribution
dstr= drec+ dZ + dpol + dhvp
Recoil
contribution
Polarizability
contribution
Charge and magnetic
dipole distribution
within the proton
Zemach radius
Hadronic
vacuum
polarization
contribution
Dominant contribution
Basic ideas
FAMU collaboration aims to measure the Zemach radius.
Expected outcomes:
 the accurate knowledge of the Zemach radius of the proton offers an efficient tool for
testing quantitatively the models of proton structure;
 comparing the values of Rp obtained in normal and muonic hydrogen might also help to
resolve the proton radius puzzle.
Laser system (INFN Trieste):
Q-switched Nd:YAG laser at 1064 nm;
Cr:Forsterite laser at 1260 nm;
DFG in a nonlinear crystal;
l = 6.776 mm
pulse duration of 10 ns;
pulse energy of 2 mJ;
rep-rate= 50 Hz.
mRIKEN-RAL muon facility
INFN Bologna
Two-step process
X-ray emission
Our contribution
 Design, development and test of an optical cavity suitable for
the FAMU experiment
 Absolute frequency measurements in the mid-IR
The need of an optical cavity:
E = 5 mJ
T = 70 K
S = 1/1000 cm2
P = 0.5
 Reduce the cross section by squeezing the laser by a factor of k
 Place the H2 target within a multipass cavity with k passes, thus preserving the
irradiated target volume unchanged
 1000 optical passes would be necessary for k=1000
Molecules & Precision Measurements
Research Group
Antonio Castrillo
Luigi Moretti
Maria
Domenica
De Vizia
Eugenio
Fasci
Our “mission”
Quantitative Laser spectroscopy:
- to test ab-initio calculations on simple molecules
- to test line shape models
- to perform fundamental metrology
- to study collisional effects
- to measure thermodynamic quantities
.....pursuing high precision and high accuracy!!!
Examples of cavities recently developed
input
mirror
quartz
spacers
PZT
mirror
The cavity of the
CREMA collaboration
The cavity of the CREMA collaboration
y
y
x
z
 670 reflections, limited by the reflectivity of the mirrors
 Mirrors’ reflectivity: 99.89 % at 6 mm with Ge/ZnS coating on a fused silica substrate
 Curvature of mirror #2 = 110 mm; curvature of mirrors at edges of mirror #1 = 100 mm
The formalism of ABCD matrices
In the paraxial approximation, the
transit of a beam (or its reflection)
through (or by) an optical element
can be described by a simple 2 x 2
matrix:
 rout   A B  rin 

  


 out   C D in 
An important application of this
formalism:
BOUNCING of a ray between two
spherical mirrors.
Stability conditions
Stability conditions
Simulation of beam propagation
xy plane
Cavity stability condition:
æ
d ö
0 £ ç 1£1
÷
è Rend ø
ìïd = 25 mm
í
ïîRend = 100 mm
yz plane
1
 z   1 0  1 d 

   



 z'   0 1  0 1   2 / Rcyl
0  1 d 


1  0 1 

Cavity stability condition:
æ
ìïd = 25 mm
d ö
0 £ ç 1í
÷ £1
R
ïîRcyl = 110 mm
è
cyl ø
N
0
 
 
Simulation of beam propagation
Intensity decay
R1=R2=0.9989
Total loss per reflection = 1.6 10-3
Gaussian beam propagation
I(x, y, z) µ e
1
l
ì 1
=
i
ï q (y) R (y) pw 2 (y)
x
x
ïï x
í
ï 1
1
l
ï
=
-i
2
q
(y)
R
(y)
pw
ïî z
z
z (y)
æ x2
z2 ö
-2ç 2
+ 2 ÷
è w x ( y) w z ( y) ø
e
é
x2
z2 ù
- êik
+
ú
R
(
y)
R
(y)
z
ë x
û
R is the radius of curvature of the wavefront
w is the width of the spatial distribution of
the beam intensity.
q is the complex curvature radius
The evolution of the intensity beam shape
during the propagation is ruled by the ABCD
law through the following equation:
q xn,1
z 
Aq xn,z  B
Cq xn,z  D
Gaussian beam propagation
Richiesta finanziaria in ambito FAMU
Attività per il 2017:
- Design della cavità ottica (attività di studio e simulazione numerica);
- Acquisizione di componenti e materiali;
- Montaggio della cavità.
Personale per il 2017:
- Luigi Moretti
(0.6)
- Livio Gianfrani (0.5)
- Studente PhD (1.0) ??
Specchi altamente riflettenti:
Montaggi di alta precisione, supporti e breadboard:
Materiali e lavorazioni meccaniche:
Software:
Missioni:
Richiesta totale:
60 kEuro
Euro 20000
Euro 15000
Euro 10000
Euro 5000
Euro 10000
Grazie per l’attenzione
H and D transitions
The frequency of any transition in the H atom can be expressed in
terms of the Rydberg constant and the proton charge radius. The
expressions are very complicated, however, the dominant
dependence on these two parameters is very simple:
The hydrogen diagram
CREMA results
CREMA - Charge Radius Experiment with Muonic Atoms
Muone m :
retrieved from Lambshift measurements in
mp atoms
massa = 105.7 MeV/c2
spin = ½
carica = -e
vita media = 2.2 µs
EXTRA SLIDES
Conclusions
 The design appears to be very robust against possible misalignments, due
to the small radius of curvature of the mirrors.
 The use of an off-axis parabolic mirror for the injection of the laser beam is
convenient since pointing instabilities will result in parallel displacements of
the laser beam, still ensuring the entrance into the cavity through the hole.
 A larger number of reflections would be possible using another coating
(such as the ThF4/ZSe coating provided by LohnStar Optics, with R larger
than 99.97%).
 The geometry should fit with the cryogenic target design.
 As for the design of a new cavity, work is in progress.....
A few examples of recent activities
kB = (1.380631 ± 0.000033) ×10-23 J/K
Examples of works using optical cavities
A molecular clock at l=1.4 mm
The cavity of the molecular clock
Input mirror:
Output mirror (PZT):
Mirror separation:
Measured finesse:
FSR:
Cavity mode width:
Beam waist:
Coupling: efficiency :
ROC=1000 mm, R=99.98%
ROC=500 mm, R=99.95%
202.3 mm
8600
740.95 MHz
85 kHz
150 µm
30%
input
mirror
quartz
spacers
PZT
mirror
Intracavity intensity = 1.6 x 106 W/m2
(for ~ 2.5 mW of incident power)
Saturation intensity = 6.67x106 W/m2
Calculated dip contrast = 6.5%.
A molecular clock at l=1.4 mm
H. Dinesan, E. Fasci, A. Castrillo, and L. Gianfrani, Optics Letters 39, 2198-2201 (2014)
Precision measurements of transition frequencies
Cavity-enhanced
Lamb-dip
spectroscopy
Fiber-based
optical frequency
comb technology
in the NIR
Absolute frequency measurements
of water vibration-rotation transitions
Test of the current knowledge of water energy diagram
A. Gambetta et al., New Journal of Physics, 2010
Current
f 0  mf r  f CEO  f beat
PZT
Absolute frequency measurements in the MIR
S. Borri et al., Optics Express 16, 2008.
P(30) line of the
CO2 n21+n3-n21 band
Some details:
PNd:YAG = 1.2 W
LPPLN = 40 mm
PSFG = 10 mW
PQCL = 2 mW
L = 23 mm
m = 5.09×10−2 D → Is ≈ 80 W/m2
Cavity Ring-Down Spectroscopy
o 
L
c( 1  R )
 (n ) 
L
c [( 1  R )   (n )L ]
 (n ) 
 0 
c 0
Alta sensibilità
CRDS to measure amount of substance
140
 = (61.50
Cavity Transmission \ mV
120
0.04)
ms
R=99.997%
F=134000
100
Leff= 37 km
80
60
40
20
0
61,85
Residuals \ mV
2
< > = 61.67 0.07 ms
Reproducibility =0.1%
61,80
0
-1
-2
61,75
Ring Down Time \ ms
1
0
200
400
600
800
Time \ ms
61,70
61,65
Measuring the amount of substance for water vapor
61,60
61,55
61,50
61,45
0
2
4
6
8
10
Label
12
14
16
18
20
RIKEN-RAL muon group
The RIKEN-RAL Muon facility
has been constructed by RIKEN at
Rutherford Appleton Laboratory
in the UK, and is now part of
the RIKEN Nishina Centre for
Accelerator Based Science. The
facility utilizes intense pulsed
proton beam provided by the ISIS
synchrotron accelerator. Thanks
to an unique superconducting
solenoid in our beam line, the
facility produces the world's
strongest source of backward
decay pulsed mu+ or mu- in the
momentum range from 20 MeV/c
to 120 MeV/c as well as surface
mu+ at 30MeV/c. A pulsed
magnetic kicker split are used to
split double-pulsed structure of
the muon beam, enabling us to
execute
two
experimental
programs simultaneously at each
channels. Important research
activities such as investigations
related to muon catalyzed fusion
and studies of condensed matter
by
muon
spin
rotation/relaxation/resonance are
now being actively pursued.