I can't link my custom jquery to wp admin

I am trying to figure out how to link a custom jquery to my custom meta box created in wordpress custom post type but I can’t find it working.

What I want to do is add a line of text when the button is clicked. But it is only reload the “add new post” page and generating a message “Post updated.” after I clicked the button.

Here is my code:

File: doubleit.js

jQuery(document).ready(function($){
  $("#btn1").click(function(){
    $("p").append(" <b>Appended text</b>.");
  });

  $("#btn2").click(function(){
    $("ol").append("<li>Appended item</li>");
  });
});

Register and Enqueue Script

add_action( 'admin_enqueue_scripts', 'add_mytweetjs' );

function add_mytweetjs() {

    wp_deregister_script('jquery');

    wp_register_script( 'jquery', 'https://ajax.googleapis.com/ajax/libs/jquery/1.6/jquery.min.js');

    wp_register_script( 'myjquerydoubler', plugins_url( '/js/doubleit.js', __FILE__ ), array( 'jquery' ) );

    wp_enqueue_script( 'myjquerydoubler' );
}

HTML Script On The Custom Meta Box

echo '<p>This is a paragraph.</p>';
echo '<p>This is another paragraph.</p>';
echo '<ol>';
echo '<li>List item 1</li>';
echo '<li>List item 2</li>';
echo '<li>List item 3</li>';
echo '</ol>';
echo '<button id="btn1">Append text</button>';
echo '<button id="btn2">Append list items</button>';

May be somebody know where is the fault of my code above.