Dynamic aperture scan in x direction with a y offset

[gwei]

Hello, Michael, and other experts,

Usually we make dynamic aperture line survey as shown in follow figure.

line survey of dynamic aperture

And we can use like follow words to get the dynamic aperture for the line (X= n*sigma_x, Y=n*sigma_y), (X= -n*sigma_x, Y=n*sigma_y)
and (X= 0*sigma_x, Y=n*sigma_y).
&find_aperture
output = "%s.aper",
mode = n-lines,
n_lines = 41,
xmin = -0.001,
xmax = 0.001,
ymin = 0
ymax = 0.0005,
nx = 21,
ny = 11,
n_splits = 5,
desired_resolution = 0.00001,
verbosity = 1
&end

But for the line (X= n*sigma_x, Y=1*sigma_y), I don't know how to make the dynamic aperture scan.
And when I make a scan with the line (X= n*sigma_x, Y=0*sigma_y), I can only get a result of NO 3 of follow figures which is not enough.

Thank you.

Guohui

[michael_borland]

Guohui,

If I understand correctly, you want to set the initial y coordinate to a fixed value and scan the x coordinate to find the aperture. You can do this by simply creating a line of particles in phase space, e.g.,

Code: Select all

&bunched_beam
	n_particles_per_bunch = 100,
	bunch = %s.bun,
	! 20mm horizontal size
	beta_x = 2e300,
	emit_x = 2e-304,
	! Zero vertical size
	beta_y = 1,
	emit_y = 0,
	! 1mm vertical offset
	centroid[2] = 1e-3
	! Distribution is a line in x-x' and y-y' phase space
	distribution_type[0] = 2*"line"
&end

In addition, in the &run_setup command, you should request the acceptance output:

Code: Select all

&run_setup
...
acceptance = %s.acc
...
&end

The .acc file will contain the initial coordinates of all particles that survive tracking, which is the aperture in this case.

--Michael

[gwei]

--

[gwei]

Guohui,

If I understand correctly, you want to set the initial y coordinate to a fixed value and scan the x coordinate to find the aperture. You can do this by simply creating a line of particles in phase space, e.g.,

Code: Select all

&bunched_beam
	n_particles_per_bunch = 100,
	bunch = %s.bun,
	! 20mm horizontal size
	beta_x = 2e300,
	emit_x = 2e-304,
	! Zero vertical size
	beta_y = 1,
	emit_y = 0,
	! 1mm vertical offset
	centroid[2] = 1e-3
	! Distribution is a line in x-x' and y-y' phase space
	distribution_type[0] = 2*"line"
&end

--Michael

Thank you, Michael

And what's the meaning of ' centroid[2] = 1e-3 ' ? a y offset=0.001 m ?
In your definition of centroid, it is
double centroid[6] = {0.0, 0.0, 0.0, 0.0, 0.0, 0.0};
And I guess {0.0, 0.0, 0.0, 0.0, 0.0, 0.0} is values in (x, x’, y, y’, t, p)
Is it right?

Best wishes

Guohui

[michael_borland]

Guohui,

And what's the meaning of ' centroid[2] = 1e-3 ' ? a y offset=0.001 m ?
In your definition of centroid, it is
double centroid[6] = {0.0, 0.0, 0.0, 0.0, 0.0, 0.0};
And I guess {0.0, 0.0, 0.0, 0.0, 0.0, 0.0} is values in (x, x’, y, y’, t, p)
Is it right?

Yes, that's all correct, except centroid[4] and centroid[5], which are in units of meters and fractional momentum deviation, respectively.

--Michael

[gwei]

Guohui,

And what's the meaning of ' centroid[2] = 1e-3 ' ? a y offset=0.001 m ?
In your definition of centroid, it is
double centroid[6] = {0.0, 0.0, 0.0, 0.0, 0.0, 0.0};
And I guess {0.0, 0.0, 0.0, 0.0, 0.0, 0.0} is values in (x, x’, y, y’, t, p)
Is it right?

Yes, that's all correct, except centroid[4] and centroid[5], which are in units of meters and fractional momentum deviation, respectively.

--Michael

So centroid[0] means x, centroid[1] means x', centroid[2] means y, centroid[3] means y', centroid[4] means t, centroid[5] means p.
if we want a centroid offset of x = 0.001 m and y = 0.001 m ,
we should write : centroid[0, 2] ={1e-3, 1e-3}. Is it right?

[michael_borland]

Guohui,

So centroid[0] means x, centroid[1] means x', centroid[2] means y, centroid[3] means y', centroid[4] means t, centroid[5] means p.
if we want a centroid offset of x = 0.001 m and y = 0.001 m ,
we should write : centroid[0, 2] ={1e-3, 1e-3}. Is it right?

That's not quite right. centroid[4] is distance traveled, not time, while centroid[5] is (p-<p>)/<p>, not p itself. The syntax for changing several centroids is

Code: Select all

centroid[0] = 1e-3
centroid[2] = 1e-3,

or

Code: Select all

centroid[0] = 1e-3, 0, 1e-3

--Michael

[gwei]

Guohui,

So centroid[0] means x, centroid[1] means x', centroid[2] means y, centroid[3] means y', centroid[4] means t, centroid[5] means p.
if we want a centroid offset of x = 0.001 m and y = 0.001 m ,
we should write : centroid[0, 2] ={1e-3, 1e-3}. Is it right?

That's not quite right. centroid[4] is distance traveled, not time, while centroid[5] is (p-<p>)/<p>, not p itself. The syntax for changing several centroids is

Code: Select all

centroid[0] = 1e-3
centroid[2] = 1e-3,

or

Code: Select all

centroid[0] = 1e-3, 0, 1e-3

--Michael

Thank you very much! Michael

Guohui